>> announcer: this is "nbc nightly news" with lester holt reporting tonight from the olympic summer games in rio. >> good evening from copacabana beach, one of the many competition sites for the games starting tomorrow here in rio. of course in this half of the world, it is mid-winter. even though we are just an hour ahead of u.s. eastern time, the sun has been down here for some time. think february in the states without the cold. we'll have more on the upcoming competition here later. but we want to start with a brand new snapshot of the race for president. a new nbc news/"wall street journal" poll shows that hillary clinton has opened up a nine-point lead over donald trump. 47% to 38%. that's up from a five-point lead just before the republican convention. and comes as the trump campaign struggles again to regain its focus after a blurring series of controversies. the latest one now involving his wife. nbc's katy tur has details. >> reporter: tonight after his toughest week yet, donald trump is trying to turn the page. training on president obama over a $400 million settlement payment to iran. >> $400 million being flown to iran. i mean, folks, what's going on here? >> reporter: but straying again claiming he saw video of iranians offloading that cash. >> that was given to us -- has to be -- by the iranians. you know why the tape was given to us? because they want to embarrass our country. >> reporter: the problem? there's no evidence that video exists. trump repeated his version even after his campaign said he was talking about generic footage from yesterday's newscast. presumably of the released american detainees landing in switzerland. and now the campaign responding to new questions about melania trump. a report on the timeline surrounding when she emigrated to the u.s. when she was a model and whether it was legal for her to work here. newly recovered photos reportedly placing her in the usa in 1995, a year before she and trump say she first arrived. melania telling msnbc in february -- >> i never thought to stay here without papers. i had visa. >> reporter: tonight firing back blasting inaccurate reporting and misinformation saying she was always in full compliance with immigration laws. >> political spouses are normally off limits but in this case trump has made such a big issue of immigration, his wife's history was bound to get scrutiny. >> reporter: all of it coming as aides, confidants, party operatives, and even supporters are pleading with trump to get back to basics. are the controversies wearing on you? >> yes, they are. but not as much as they are my wife. >> he has a good message to tell and the democrats don't. >> reporter: the trump campaign is insisting that they are getting back on message. this as new battleground polling is showing what's at stake. trump is down double digits in pennsylvania. lester? >> katy tur in maine, thank you. and for his part, president obama said today that while donald trump needed to receive intelligence briefings as a candidate, a candidate also needed to act like a president and not spread those briefings around. the president also spent a great deal of time talking about the fight against isis. we get more tonight from kristen welker. >> reporter: in a press conference at the pentagon designed to tout the obama administration's isis strategy, president obama once again jumped into the 2016 race targeting donald trump. >> i obviously have a very strong opinion about the two candidates who are running here. one is very positive and one is not so much. >> reporter: the president today asked about trump's repeated assertions the election will be rigged. >> that's ridiculous. that doesn't make any sense. and i don't think anybody would take that seriously. >> reporter: and he handed down a stunning warning when asked about trump receiving intelligence briefings which both candidates are now cleared for by law. >> if they want to be president, they got to start acting like president. >> reporter: but donald trump and republicans have also put the president on defense accusing his administration of paying ransom for americans held in iran after revelations the u.s. sent a $400 million cash payment to iran in january coinciding with the release of those americans. >> we have a president who frankly is incompetent. >> reporter: the president firing back at his critics arguing the cash was to settle a decades' old financial dispute. >> we do not pay ransom for hostages. >> reporter: kristen welker, nbc news, the white house. we're learning more about a horrific attack on the streets of london. a stabbing spree that claimed the life of an american woman from florida leaving five others injured. investigators say there does not appear to be a terror connection. nbc's kelly cobiella has more from london. >> reporter: flowers on a central london sidewalk for darlene horton. the wife of a florida state university professor stabbed in the back. a witness who took this picture said paramedics tried for 20 minutes to save her. >> you could just see they were applying a form of cpr. >> reporter: 64-year-old horton died on this sidewalk. tonight fsu's president said there are no words to express our heartache. her husband psychology professor richard wagner was teaching in london for the summer. it was their last night in the city. the couple due to fly home to tallahassee today. the man injuring five others in a stabbing spree seen on this video on the ground being restrained was mentally unstable. a national with somali descent with no ties of terrorism, no sign of radicalization, police said. >> at this time we believe this is a spontaneous attack and that the victims were selected at random. >> reporter: the city already on alert for terrorism. you said it was chaos. >> it was chaos. because nobody knew what was going on. >> reporter: tonight praise for the action of police on scene in just six minutes. the suspect quickly spotted, tased, and restrained. sadly too late for a florida family now grieving for a wife and mother. kelly cobiella, nbc news, london. as miami deals with a home grown zika outbreak, the cdc said today that more than 1,800 americans have now been diagnosed with the virus after catching it overseas. including 479 pregnant women. at his news conference, president obama sharply criticized congress for going on recess before authorizing more funding to fight zika. meanwhile in florida, concern remains high about how far the spread of the virus may go. kerry sanders has the latest. >> reporter: pregnant mothers to be in florida have been promised free zika tests. yoland baptiste four months pregnant is among the lucky first. women were told today no testing here, try another office. >> i'm concerned, yes. because this is my first pregnancy and i want it to be a successful one. >> reporter: rather than wait for the state, tracy humphries went to quest diagnostics, a private lab for testing. her husband did too. >> if i do see mosquitoes and i think i have any bites, i would get tested again. >> reporter: zika test results take two to seven days and in many cases may have to be repeated. today president obama criticized congress for failing to fund zika before taking a seven-week vacation. >> zika is a serious threat to americans. especially babies. right now. so once again i want to urge the american people to call their members of congress and tell them to do their job. >> reporter: some good news today. two days now and no more home grown zika cases. the cdc here today clarified the area where the zika mosquitoes are could be as small as 500 square feet. the challenge, making sure those mosquitoes don't bite people who then leave spreading the virus elsewhere. kerry sanders, nbc news, miami. let's turn now to news breaking here in rio. the international olympic committee just announced how many russian athletes will be allowed to compete. a third of the country's team has been banned after a major doping scandal. it comes on the eve of opening ceremony as this city remains cloaked under a massive security force. the largest ever deployed in brazil. nbc's miguel almaguer is with athletes and the military. >> reporter: tonight for team russia in rio, a split decision for many athletes appealing a ban after a widespread doping scandal. >> the message is clear. there is no place to hide for cheats. >> reporter: russian boxers, volleyball players, and many members of the swim team given the all clear to compete late today. >> i think i would be naive to think i haven't ever competed against somebody who has done something that was against the spirit of sports. >> reporter: while rio is iconic for its incredible views, tonight what's most stunning here is security. at the foot of christ, heavily armed soldiers. even along the sands of copacabana, police looking for threats big and small. robbery is the biggest crime down here? >> yeah. >> reporter: security remains tight along the olympic torch route. after days of protest, today few problems in this city of sand and surf. the torch one wave closer to the cauldron as tonight the world watches rio. just 24 hours until opening ceremonies. we expect half a million people to flood beaches like the one behind us here as well as this entire city. leer, with this doping scandal, another layer of drama before the games get under way. of course the biggest sporting events, the most exciting ones are still days away. >> here we are. thank you very much. the u.s. is represented by 554 athletes here in rio. 292 of them are women. the most women who have competed for any country. tonight as we take a closer look at some of the athletes to watch, it is the american women leading the way. the usa women's soccer team's 2-0 win over new zealand yesterday sets them on the right path to clinch their fourth gold medal. and underscores the continued dominance of american women. >> in london more american women won gold than american men. women's basketball, they dominate. the williams sisters, they both won four gold medals. they can both win in singles and doubles. >> reporter: i met up today with nbc olympics broadcaster mary carillo to talk about which athletes could make big headlines here. now, individually, behind us is the swimming venue. we didn't think we'd see michael phelps here. >> no. he said he was done in london. he'd already won 22 olympic medals. 18 of them his favorite color, gold. now he's come back and he's got a chance -- he's got a very legitimate chance of taking on maybe three more golds. >> reporter: and don't forget the splash american katie ledecky made four years ago. >> she comes into london as a 15-year-old, wins the 800 free style, stuns the world. >> the future of usa swimming. >> reporter: four years later, she could win a fist full of gold. she wins by jaw breaking margins. >> reporter: in gymnastics, mary says watch out for american newcomer simone biles. >> i'm telling you, this kid. she's got real heft to what she does. and she does things that nobody else has ever seen before. >> reporter: and mary says don't count out jamaican sprinter usain bolt. >> yeah. he's a little bit dinged up, but he is as big a presence as anyone. >> reporter: this is olympics number 13 for mary who has extra reason to love the rio games. >> i've been watching so much television, so much political fighting and you hear the candidates saying this is what america represents. i love the idea the american flag is going to go up for the next 17 days and people have relief from all that political fatigue. i don't have to tell you what that's been like. >> reporter: can i hug you and say mary carillo for president? that's my endorsement. mary carillo of nbc olympics with some pretty great perspective there. ahead of tomorrow's official opening of the summer games. still ahead tonight, making sure u.s. olympic athletes stay clean. our exclusive look at a surprise drug test being carried out. also why ford has issued a huge recall. the potential problem with almost a million vehicles. back now from rio de janeiro. in the run-up to these games, doping has loomed large. as we reported a few minutes ago, there's been numerous athletes and entire national teams under the glare of the spotlight. tonight we're taking an ideas look at the u.s. anti-doping agency and why its chief believes usada is the best in the world at detecting cheaters and working to ensure that american athletes are the cleanest. here's nbc's ron mott. >> is there any stopping lance armstrong? >> reporter: the old adage cheaters never win has been debunked time and again in sports. they do win and sometimes even get caught. >> unbelievable! >> the win at all costs culture is across the globe. >> reporter: travis tigert, head of the u.s. anti-doping agency or usada is on a mission to make sure american athletes never use drugs to cheat. looming over the rio games, a doping scandal. russia's entire weight lifting team and all but one track and field athlete banned. >> the pressures that are put on athletes to do whatever it takes to literally stop at nothing in order to achieve success is as great as we've ever seen. >> reporter: here in the u.s., athletes are tested at competitions and away from their sport. it's a system bolstered by the element of surprise. nbc news is with a usada doping control officer who showed up unannounced at 7:00 a.m. to collect a sample. >> we don't want the athlete to be prepared for us coming. >> reporter: this marathoner answered the door. his 115th usada drug test had just begun. >> you got nothing to hide, there's nothing to worry about. >> reporter: at the u.s. olympic diving trials, david got word his test was due. after just making the team, a usada official never losing sight of him for nearly an hour until the sample was obtained. >> they make it really easy on the athletes but they also make sure all their t's are crossed and i's are dotted. >> reporter: of the thousands of american athletes tested by usada each year, dozens are sanctioned. more than 100 since 2013. sprinter justin gatlin failed a 2006 drug test and served a reduced penalty in exchange for cooperating. tyson gay was also suspended after a positive test in 2013. both denied knowingly taking a banned substance. both competing in rio. travis tigert believes in second chances though his number one priority is leveling the playing field. >> obviously we have to hold individual athletes who cheat accountable. but getting to the root cause, the system of the win at all costs, those are the leaders within the sport. team doctors, trainers, owners who may be pressuring athletes. those are the ones we're doing our best to hold accountable on a daily basis. >> reporter: obviously there will be a lot of eyes and attention on the russians allowed to compete here in rio. today the head of the international olympic committee said more than 5,000 tests will be administered and they're going to keep them on file for ten years for reanalysis. >> all right. ron mott tonight, thank you. when we come back, charges of extortion, fraud, and even worse as dozens of reputed mobsters are indicted. federal agents today arrested nearly four dozen men accused of being part of the mafia and running a vast east coast criminal operation. in what officials are calling a significant blow to the mob, the fbi rounded up what it said was leaders and members of the gamibino, bonanno, genovese, and lucchese families. the fbi says the families jointly ran an operation in five states involving illegal gambling, fraud, arson, and extortion. ford today is recalling more than 800,000 vehicles because their side door latches might break and the doors could open while the vehicles are moving. the model years involved are 2012 to 2015 and they include certain ford and lincoln suvs, cars, and vans. when we come back tonight, matt lauer with the most decorated american athlete of all time. michael phelps speaks out about his triumph and his personal struggles. ===janelle/vo=== a rare look at the situation room where law enforcement agencies will monitor the entire city. ===raj/vo=== plus ...nbc bay area responds to a common scam involving the i-r-s. what to do if you get a call. ===raj/next close=== next. the olympic rings lit here in rio and finally tonight, he is sure to be one of the most talked about athletes of these games. michael phelps taking the plunge for what he says will be the last time. and though he looks more or less the same as he did four years ago, the story may be in what has changed on the inside for michael phelps as he prepares to carry the american flag tomorrow night at the opening ceremony. matt lauer caught up with phelps. >> reporter: from sydney and athens to beijing and london -- >> here comes phelps to the wall! >> reporter: -- michael phelps has won 22 olympic medals. more than anyone else in history. >> and michael phelps is going to win gold! >> reporter: in public he owned the spotlight. but privately phelps struggled deeply. >> 100% i was lost. i thought of myself as just a swimmer and nobody else. >> reporter: now 31, the swimmer is a different person than the one we've come to know. >> i'm a lot more laid back, i'm a lot more relaxed, i'm a lot more open. >> reporter: his cheering section is different too. phelps' sisters and mother who've been staples in the stands are now joined by his fiance and their son boomer robert phelps. >> phelps is going to win it. >> reporter: at 2 months old, boomer saw his father compete for the first time -- >> looked like boomer was awake for the race which was good. >> reporter: -- and qualify for his fifth olympics. >> having my first born be able to watch or be able to be there as i compete in my last olympics is something that's special. >> reporter: boomer's middle name is in honor of his coach robert bowman who he's trained with since he was 11. he's like a completely different person. >> absolutely. in all the areas. it's all about the swimming now. >> reporter: that wasn't the case going into london. >> leading into london, i didn't want anything to do with the sport. >> reporter: in fact, phelps hated swimming. and often wouldn't show up to practice. but he and bowman put on a good front keeping their strained relationship hidden. prior to london, bob, was there a time you thought he wasn't going to go? >> yes. >> reporter: you thought he'd quit? >> yes. i hoped he would. >> reporter: why? >> i thought it was going to end badly. >> reporter: it all came to a head in 2014 when phelps got arrested for his second dui and went to rehab. >> i felt like i didn't want to see another day. i felt like it should be over. >> reporter: so did you check yourself into treatment because you had a drinking problem or because you had a public relations problem? >> i checked myself in because i think i was at a point in my life where something needed to change. >> reporter: he's sober now and there's a sense of self-acceptance. >> ready? go! >> reporter: people close to phelps say he hates to lose more than he loves to win. so out of rio, what's realistic? >> there's a number in my head. >> reporter: so if you don't hit the number, will you be able to look at me and say i went out the way i wanted to go out? >> yeah. because i'm giving an honest effort. i'm having fun again. and this is something that i haven't had in a really long time. >> reporter: there's no question he's always had that competitive fire. but this time he also has the passion. matt lauer, nbc news, rio. and that is going to do it for us on this thursday night from rio, our home for the next couple of weeks. glad to be here. i'm lester holt. for all of us at nbc news, thank you for watching and good night. outcue: chop from t from the top trt:03 ==raj//con't vo== right now at 6 -- justice halt gridlock at a south bay courthouse as workers hit the right now at 6:00, justice halted. gridlock at the south bay courthouse as workers hit the picket lines again. the news at 6:00 starts right now. thanks for joining us on this thursday evening. >> it's a nightmare at the courthouse. day two of the workers strike. everyone from criminals to people just trying to fight traffic tickets are noticing. damian, people must be frustrated there. >> reporter: very frustrated. a lot of frustration here at the hall of justice today. there have been no negotiations and none scheduled so far. i spent the morning in department 24 in the basement. what i saw today was a lot of confusion. white the clerks spent the day chanting, inside department 24, it was borderline chaos. >> it was tough. it was tough today without them. weary l rely on them. >> reporter: they didn't have staff available to process our request to put a camera in. i witnessed a judge struggling to process a case. >> the judge was saying, which color copy of the order does the defendant get? where do i write the fines on here? a judge doesn't know how to fill out the paperwork. >> reporter: the confusion meant families of inmates wasted a day in court because judges could not address their cases. >> that's my son. my son's case.