good evening. we begin with a historic interview 40urs ago. president obama speaking exclusively to abc news' robin roberts and announcing something that no u.s. president has ever said that he supports same-sex marriage. for years, he only supported civil union, saying his position on marriage was evolving. last weekend, vice president biden surprised everyone seemingly to endorse gay marriage. and today, the president himself told robin how and why his opinion has changed. >> i have always been adamant that gay and lesbian americans should be treated fairly and equally. and i was sensitive to the fact that for a lot of people, the word marriage was something that evokes very powerful traditions, religious beliefs and so forth. but i have to tell you that over the course of several years, as i talked to friends and family and neighbors, when i think about members of my own staff who are incredibly committed in monogamous relationships, same-sex relationships. when i think about soldiers or airmen or marines or sailors throughout fighting on my behalf and yet feel constrained, even now that don't ask, don't tell is gone, because they are not able to commit their semiing in a marriage, at a certain point, i just concluded that for me personally, it is important to me and go ahead and affirm that i think same-sex couples should be able to get married. you know, it's interesting. some of this is also generational. malia and sasha have parents that have same-sex couples. there are times around the dinner 25ib8 we are talking about their friends and parents and malqulee and sasha, it couldn't dawn on them that some how, their friends' parents would be treated differently. it doesn't make sense to them. and that is the kind of thing that prompbts a change in perspective. >> did you discuss this with mr. obama? the same-sex issue? >> i did. this is something we talked about over the years. and she feels the same way that i do. and that is that in the end, the values that i care most deeply about and she cares most deeply about is how we treat other people. we reboth practicing christians and obviously, this position may be considered to put us at odds with the views of others. but, you know, when we think about our faith, the thing at root that we think about is not only christ sacrificing himself on our behalf but it's also the golden rule. treat others the way you want to be treated. >> in a interview, robin. what happened what about vice president biden. everyone presumed that the vice president forced the president's hand. did you talk about him? >> i did talk about him. it was an authentic response when the president said he is comfortable with same-sex marriage and this is a discussion they had been having, that could have had prior to the election and the vice president may have had a hand in jumping the gun just a bit. >> everyone says, bide listen be biden. right? >> the president said that himself, yes. >> all right, robin. as we said this is a historic cultural and political event in this country. head on back to new york. great interview, thanks. >> thank you. as we said, the president's decollar ration lands in the center of the culture wars in the country. republican mitt romney was quick to weigh in. the latest poll shows that 52% of us support gay marge. and jake tapper is going to break down who does and doesn't by age and ethnicity, starting with the man ready to challenge the president in november. >> campaigning in oklahoma this afternoon, mitt romney says he disagrees with the president's situation. >> i believe marriage is a relationship between a man and a woman. but but he speak gingerly. >> this is a very tender and sensitive topic as are many social issues. i have had the same thoughts since i started running for offense. >> reporter: on twitter, ellen degeneres placed the president for his words. and andy and todd celebrated with her twins. >> it's a very, very brave move to make and we are extremely grateful. >> we realize what a politically risky position he has put himself in. >> almost half the country disagrees. a divide generational. poll shows most americans under the age of 40 support same-sex marriage. most over the age of 65 oppose it. a racial gap persists as well. a majority of whites are supportive. a majority of african-americans oppose. such as charles robinson in virginia. >> a man is supposed to be a woman and a woman is supposed to be with a man. that's how i feel and that's never going to change. >> reporter: virginia is one of 30 starts whose voters have groan to the polls and cast bat lots against same-sex marriage. he said, it felt good. it was the right thing to do. jake tapper, abc news, the white house. >> i want to bring in co-anchor of ""good morning america," "this week," what about is it? is it going to cost the president in november? >> it could. and in key states like ohio, wyoming, and iowa. other the other hand, it could help the voters. and the white house is counting on that. the most part, the white house doesn't want to make a big deal of it. they know most voters don't want to make a big deal. the voters seem to punish whoever seems to bring up the issue the most. >> don't expect romney to bringt up over and over. >> he talked about it gingerly today. >> we heard that the president told robin, how about it? >> this was not a plan. there is no way this was a plan. this is matter of core conviction. i wouldn't send someone else out to make that decision. but it showed -- you couldn't seem to be evolving in an election campaign where it's going to come up in debates and across the trail. >> i speeded it up. >> i want to tell everybody again, you can see more of robin's interview tonight on "nightline" and tomorrow on "good morning america.." tonight, the terror threat revealed this week. the new bomb behind al qaeda. the man behind it, the master bock maker is still in hiding, still at work. recordedly helping to implant explosives in people and pets. abc's chief investigative correspondent brian ross has more. >> reporter: at the age of only 30, ibrahim al asiri has now emerged as the most feared face of terror for american authorities. the master bomb maker behind the efforts of al qaeda in the arabian peninsula to blow up a u.s. passenger jet. >> al qaeda affiliates, especially al qaeda in the arabian peninsula represent the top counter terrorism threat to the nation. >> reporter: it includes bombs in pets, hiding in aircraft, in cameras and in hard drives that could explode when plugged into an operational computer. >> he has a savvy that is useful for an al qaeda operative. >> reporter: a saudi citizen who studied chemistry in college, al asiri's parents say he became radicalized after the death of a brother. >> he hates american ideology, he hates western values. >> reporter: the u.s. has expanded its drone operations in yemen. they have survived at least one drone strike in the last year. >> we want to make sure he doesn't continue to build any device or impart his knowledge to everyone else. >> reporter: while the latest plot was foiled, authorities tell abc news there are several plots aimed at u.s. airlines that are in the plans stages, if not further along. tonight, the fbi continues to pour over the latest bomb, the one brought out by the double agent working for the cia and others. the threat from al qaeda remains very real and active. >> brian, thank you. now we turn from national security to the national economy. and another tough day on wall street. the sixth straight day of losses. the dow down nearly 100 points, making it the longest losing streak since august of last year, fueled by more signs of economic trouble out of europe. and once again, there was a drama on folding in that north carolina courtroom where former president rnl candidate john edwards is on trial. today, one of elizabeth edwards' friends took the stand about how the drama affected elizabeth before her death. >> reporter: the most emotional point of the day was when jennifer palmieri, a friend of edwards, described her last days before he died of cancer. she was worried when she died, there would no be a man around who loved her. she testified of private meetings about hunter. she said she was in a meeting with edwards and his wife and benefactor lisa blue who admitted flying rielle hunter to los angeles to go shopping in. was new to elizabeth. she was really upset. she didn't understand why they would be helping hunter, since she understood the affair was well over. it makes edwards look more and more guilt. a year before, john edwards told me on "nightline" he was in the dark. >> i don't know what his reasons for for doing it. >> reporter: the prosecution says it's ends its case tomorrow. the last three witnesses will be three fbi agents and one for financial supporter of edwards' campaign. one that is missing from that list is rielle hunter. now it's up to edwards' defense to call her in to testify. >> if they do, thank you bob woodruff. and a legal settlement to tell you about tonight. arising out of the tragedicy in philadelphia. a badge charging into the tourist boat. the families of the two tourists who died will be splitting $15 million. the owners of the toushist boat and the tug boat agreed to make the payments. coming up here, what the government said today about x-rays. the age in which they begin and how many are too many in a lifetime. not in this economy. we also have zero free time, and my dad moving in. so we went to fidelity. we looked at our family's goals and some ways to help us get there. they helped me fix my economy, the one in my house. now they're managing my investments for me. and with fidelity, getting back on track was easier than i thought. call or come in today to take control of your personal economy. get one-on-one help from america's retirement leader. the abrasives in the toothpaste actually create those 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[ laughs ] [ male announcer ] ask your doctor if chantix is right for you. it's the time of year a lot of students work very hard to get their degrees, but one graduate gives new meaning to hard work. think of the movie "good will hunting," a janitor with a quiet dignity and a dream. for 19 years cleaned the classrooms at an ivy league school and now is garage w5i9ing at the top of the class. here is abc's john berman. >> reporter: for nearly 20 years he has mopped the floors, cleaned the bathrooms, carried the trash. but this sunday gac filipaj, a janitor at columbia university, has other plans. >> this sunday, thank god, finally i'm going to graduate. >> reporter: 52-year-old gac filipaj is graduating from columbia with honors. >> i prove that i have enough strength to finish what i started to do. >> reporter: he pled to the u.s. from yugoslavia in 1992 to escape the civil war. he spoke -- >> no english at all. >> reporter: he landed the job as a custodian at columbia and after 7 years of english classes was accepted at the university. he would take classes in the morning, than work an 8 hour shift into the night. nothing about it was easy including his major classics. >> very difficulty, especially ancient greek. >> he was immensely proud of doing a good job as a custodian, but doing a equally good job in the classroom. >> reporter: he says he plans to keep his job for now. what he really wants is a phd. what do you think it is going to feel like for you here when you finally get that diploma and are sitting in this green at graduation? >> i don't know. probably it will seem to me as if i woke up out of a dream, a nice dream. >> reporter: a dream for gac for the rest us an inspiration. congratulations. >> he said he could like to find another job some day, but wants everyone to know, he takes pride in his work as a janitor. thank you for watching. watch more of robin and the president on "nightline" later. see you tomorrow night. ♪ [ male announcer ] for our families... our neighbors... and our communities... america's beverage companies have created a wide range of new choices. developing smaller portion sizes and more low- & no-calorie beverages... adding clear calorie labels so you know exactly what you're choosing... and in schools, replacing full-l-calorie soft drinks with lower-calorie options. with more choices and fewer calories, america's bevere companies are delivering.