stunning new images, widespread flooding across three states, neighborhoods devastated in south dakota, streets completely caved in, homes and vehicles washed away and teetering on the edge. in minnesota, officials confirming a partial failure at a dam southwest of minneapolis. where in the storm zone tonight. also this evening, just two days before the joe biden and donald trump debate, the final preparations and our new reporting, could mr. trump announce his vp pick before the debate? wikileaks founder julian assange boarding a plane to freedom. the plea deal he struck to end his years long standoff with the u.s. government for publishing a trove of classified documents. the deadly violence in kenya police opening fire as thousands stormed the parliament. what's driving these protests? nbc news investigates the search for more than 50 migrants with possible ties to an isis affiliated smuggling network, released into the u.s, their whereabouts unknown, and the american track star overcoming life's hurdles for his shot at gold in paris. this is nbc nightly news with lester holt reporting tonight from aspen, colorado. good evening from aspen, colorado, where thought leaders have gathered for the aspen ideas festival, of which nbc universal is a media partner. we'll tell you more on that later. but let's begin with the flood emergency unfolding across south dakota and minnesota. while there has been some relief in iowa, stunned residents elsewhere have been powerless to stop the surging floodwaters from spilling into their neighborhoods. the rising rivers riding history along the way as waterways across the region hit record crests in minnesota that broken dam holding communities in terrifying suspense tonight, while brutal heat holds its grip across a wide area of the country, 70% of the nation experiencing highs of 90 and above. adrian broaddus has our report tonight. catastrophic flooding across the midwest in south dakota, neighborhoods off the big sioux river are unrecognizable, with streets completely caved in and people unable to access their homes. some cars washed away. others are teetering on the edge of those collapsed roads, and the water is still gushing. in minnesota, entire communities are submerged. we literally watched our childhood wash over the bank. trees, buildings. residents near mankato are bracing for the possible failure of the rapid dam. oh my god, that's her life. jenny barnes grew up here. her father and brother live in this house by the river. we're hanging in there. our house is hanging by a thread. it's not just their home they're worried about. the family has owned the dam store for more than 50 years. that's what we worry about the most. the store. we know the house is gone. we know we'll never be able to go back in that house. but let's keep the dam store. that's the main goal. but that's our business. that's our livelihood. and in sioux city, iowa, the water levels are going down. residents aren't out of the woods yet. shaquille brewster is there. 24 hours ago, this road was completely flooded. the water here is clearly receding, but you see, the big sioux river is still at historic levels, rich and amy evacuated their mother overnight. how weird is it to be this close to the house, but not able to access it, right? it's very, very. yeah. devastating is a good word. it's right there. yeah, it's within reach, but it's not within reach. with a strong line of thunderstorms already wreaking havoc across michigan today, more rain is set to return here by the end of the week. adrian, that's a dramatic backdrop. we're looking at. the rain has stopped, but i know there are still dangers out there. lester. that's right. and city officials are pleading with people to stay away from the rushing water. folks have been trying to get pictures of this scene all day. officials say even though the ground looks stable, it's not. and officials warn if someone were to accidentally fall in, there's no way first responders could go in for a rescue. lester adrienne broaddus thank you. tonight, with the first presidential debate just two days away, we're learning that former president trump could announce his running mate earlier than expected. kelly o'donnell is at the white house. kelly, what more do we know about the potential timing here? well, lester, the choice of a vp nominee is one of the big unknowns. and four sources familiar with the situation say there have been high level discussions about moving up the timeline. mr. trump has talked about publicly from before the convention to as early as this week to make a splash. contenders are said to include north dakota governor doug burgum and senators jd vance and marco rubio, all expected to be in atlanta for the debate. and now, turning to an issue that could come up on the debate stage, student loan relief and one of president biden's programs is facing new legal challenges. tonight, a campaign promise aimed at millions of student borrowers hangs in the balance. we made a commitment to fix our broken student loan system. one of president biden's programs to slash student loan debt is partially on hold after two federal judges temporarily blocked further relief from what's known as the save plan. 8 million borrowers are enrolled in the program that ties the amount of loan repayment to income and family size. under its rules, about 4 million borrowers qualify for no monthly payment. others get a deep reduction. austin davis is a special education teacher who says he and his wife, brooke, saw their monthly payments drop from nearly $1,600 down to $480. without this, we would not have been able to afford the cost to be able to have our own house to live with our daughter. two separate lawsuits were brought by republican attorneys general across 18 states, arguing that the education secretary overstepped his authority and that states holding loans could be harmed. the president has no textual basis in law for this plan, and i'm not going to let joe biden saddle working missouri families with ivy league debt. education secretary miguel cardona late today. people shouldn't have to choose between groceries and, the student loans. some republicans are working harder to stop what we're doing to help than to offer any solutions. the administration says it intends to vigorously defend the relief program. kelly o'donnell, nbc news. the white house and join us for complete coverage starting thursday night of the first presidential debate hosted by cnn. turning overseas now, the founder of wikileaks, julian assange, has arrived on the northern mariana islands, a u.s. commonwealth in the pacific, where he'll appear before a federal judge to finalize his plea deal for conspiring to hack u.s. secrets. keir simmons is following this for us. keir what more do we know? reporter well, lester, julian assange spent the day traveling video released by his team documenting his journey today on a private jet from the u.k. to bangkok and finally to the northern mariana islands, where he's just landed and will appear in a us court. the justice department's 18 charges against him, including conspiring with army intelligence officer chelsea manning to hack us secrets. reduced to just one plea deal and he will get credit for time served five and a half years in a uk jail. in 2010, assange's wikileaks released a trove of material, including details of the killing of civilians in iraq and afghanistan. this, the end of a long standoff. his next stop will likely be australia, where his wife and children are waiting for him. lester all right. kira. thank you. in kenya tonight, deadly chaos in the streets after rioters stormed parliament with police opening fire. andrea mitchell has late details. issa tonight. police firing on thousands of unarmed protesters, killing at least five and wounding dozens after protesters stormed the kenyan parliament over a proposed tax law setting fire to parts of the building. as legislators fled in the melee, former president obama's half sister alma obama, a self-described activist talking to cnn young kenyans are demonstrating for their rights. they are demonstrating with flags and banners i can't even see anymore. there instead of being tear gassed, the uprising over a $2.7 billion new tax bill as kenya struggles to pay down its debt from covid, the ukraine war and two years of drought. but young people are furious with the country's president, william ruto, elected less than two years ago on a promise to help the poor. tonight's violence shattering the glittery image the world saw just last