Transcript for Post midterms, Sessions out in stunning resignation, some races too close to call
Last night the Republican party defied history to expand our senate majority. Reporter: After a momentous midterm election, an extraordinary and at times contentious presidential press conference -- Sit down. You didn't answer my question. You are the enemy of the people. Reporter: President trump celebrating what he called a near victory in yesterday's vote. And hinting at political shakeups in his cabinet. I will say that for the most part, I'm very, very happy with this cabinet. Reporter: And less than an hour later, a bombshell announcement. Today the president demanded his attorney general, Jeff sessions, resign. Reporter: Jeff sessions, the embattled attorney general, forced to step down from his post. Submitting an undated letter saying, dear Mr. President, at your request I'm submitting my resignation. I've been honored to serve as attorney general. Jeff sessions was fired by president trump. Make no mistake. And this means that the president is ready to get involved as he wanted with his justice department, maybe up to and including Robert Mueller's probe. Reporter: After meeting with his staff, he exited the justice department today to applause. Early on, sessions stunned and infuriated the president by recusing himself from the Mueller probe, citing a doj regulation that bans employees from taking part in an investigation if they know the people involved. Therefore, I have recused myself in the matters that deal with the trump campaign. Reporter: After today's resignation, the president swiftly announcing his replacement on Twitter, appointing sessions' chief of staff, Matthew Whitaker, as the acting attorney general. Whitaker will now take oversight of the Russia probe. Just last year, Whitaker wrote a CNN op-ed called "Mueller's investigation is going too far." In an appearance on CNN, Whitaker defended the infamous trump tower meeting. We have no information right now that would suggest that he knew who this individual was that he was meeting with. Reporter: Democrats are crying foul, calling for Whitaker to recuse himself because of his previous comments attacking the Mueller investigation. There's no question that now that Whitaker is running the Russia investigation, he will likely constrain it in a significant way. Reporter: But tonight on pbs, kellyanne Conway denying that president trump intends to use Whitaker to stop Mueller. So does this mean the president expects Mr. Whitaker to shut the investigation down or to limit it? No. That is not the reason that the president has asked Matt Whitaker to step in as acting attorney general. Reporter: The shakeup occurred on the heels of a seismic shift in congress. With the country now looking to see how the president will govern in the wake of democratic control of the house. I think president trump knows that he is in a politically perilous position. And he needed to act and potentially act very fast. Reporter: As a staunchly conservative senator from Alabama, sessions was an early supporter and adviser of then candidate Donald Trump. When few were supporting him. He is the one person I sought his counsel, because he's been so spot-on. He's so highly respected. Has anybody ever heard of senator Jeff sessions? Reporter: A movement that led to a budding bromance. I am pleased to endorse Donald Trump for the presidency of the United States. Reporter: And in his speech on election night, trump credited sessions with helping lead him to victory. He's as smart as you get. Senator Jeff sessions. Reporter: Sessions was one of trump's first cabinet appointees, just ten days after the inauguration. So help me god. Reporter: Sessions' recusal soured his relationship with the president, eventually leading to bitter public outbursts, questioning his ability to do his job. If he was going to recuse himself, he should have told me prior to taking office. And I would have quite simply picked somebody else. Reporter: Sessions' deputy, rod Rosenstein, was put in charge of the Russia probe. After the president fired FBI director James Comey. For the past year the president continued to lash out against sessions, tweeting, why aren't the committees and investigators, and of course our beleaguered A.G., looking into crooked Hillary's crimes and Russia relations? Horrible. Jeff sessions -- If the justice department doesn't take action -- I'm really not involved with the justice department. I'd like to let it run itself. Reporter: While rumors swirled about growing strain between the pair, sessions put on a brave space, speaking to ABC's Pierre Thomas. How is your relationship with the president? We're getting along. Reporter: Their fraught relationship becoming frequent fodder on "Saturday night live." I'm a sneaky, lying little villain. If mean old Mr. Mueller comes after me, I'm just going to roll over and play dead. That's very funny, Mr. President, but I'm not going anywhere. Reporter: In recent months the president began implying that sessions' days as the head of the justice department were numbered. Speaking to "Fox & friends." I put in attorney general that never took control of the justice department, Jeff sessions. Never took control of the justice department. Reporter: He would tell Bloomberg news that sessions would be safe, at least until the midterm elections, which brings us to that press conference today. I'll tell you, there will be changes. Nothing monumental from that standpoint. I don't think very much different than most administrations. And we have -- I mean, we have many people lined up for every single position. Any position, everybody wants to work in this white house, we are a hot country. This is a hot white house. Reporter: And the trump administration's turnover rate has been dramatic. 26 high-profile officials have either been fired or resigned in less than two years. This has been a presidency marked by turnover. Top officials have been indicted in some cases, have resigned, have moved on, have been replaced in an unprecedented clip. Reporter: Today's drama in Washington threatening to overshadow the results of the midterms. Democrats adding 29 seats, securing a house majority. And Republican gains in the senate locking in their majority through 2022. The big takeaway is that Democrats control the house. For the first time in Donald Trump's presidency. Reporter: For Democrats, these are the spoils of victory. They can now launch investigations, issue subpoenas, even demand tax returns. We now have an opportunity to get the documents that we need to do our investigations. The constitution mandates that we be a check on the executive branch. Reporter: The president ready to fight back. They can play that game, but we can play it better. Reporter: All this as election results continue to trickle in. While the Democrats notched at least seven wins for governor, tonight nearly a dozen house seats and three senate races remain undecided. The blue wave may not have been a tsunami. But the pink wave ushered in over 100 women to the house represents. A new record. Among them, several veterans like former Navy pilot and federal prosecutor mikie Sherrill in New Jersey. I'll never stop fighting for you and for the generations of Americans that have laid down their lives for our freedoms. Reporter: The mother of four deciding to run as the antithesis to trump and his policies. Mikie Sherrill? She is going to win. Reporter: And last night, those dreams coming true. Mikie taking to the stage with her entire family. It's so incredibly exciting. We've worked so hard for this. Reporter: Across the country the victories weren't just female, they were diverse. An amazingly diverse array of experiences that I think reflect the diversionty of the American people in a way we haven't seen before in congress.
This transcript has been automatically generated and may not be 100% accurate.