Transcript for The Year 2018: Drama in politics

I think people like me. A president unlike any other. How do you impeach someone is doing a great job? What a force of nature. Anybody that thought they're going to get something different than what we've gotten is kidding themselves. When I can, I tell the truth. I watch the news every day. I think I'm a great moral leader. Every day, you're like, he couldn't possibly top that. I've only run once. And that was for president, and I won. How did that happen? And he does. I say, don't worry about it. I'll just figure it out. Donald Trump's every move, must-see TV. When I put this hat on, it made me feel like Superman. He can speak for me anytime he wants. The space force. It will go E.T., yoda, then Groot. At the end of his second year, trump is on defense. The Mueller investigation closing in. Democrats taking the house. His administration in a constant state of upheaval. You look at the operation of this white house, let's hope to god we don't have a crisis. All year, west wing drama filled the pages of best-selling books. There were times when Donald would say something so insane. The book is a work of fiction. I think he's morally unfit to be president. The "New York Times" op-ed revealed dissension in the ranks. The biggest issue they're going to have is figuring out who wouldn't have written a letter like that. If I had 12 days, I would have fired more people. You had to get these people out of there that didn't like the president. John Kelly, pushed out. Mick Mulvaney filling in. This year alone, more than two dozen top administration officials either fired, pushed out, or resigned. We learned of the bombshell resignation of general Mattis, who will leave in February. If you work in trump's cabinet, put your resume in other places. Trump felt the heat as Robert Mueller's investigation zeroed in, indicting 12 Russian military intelligence officers, revealing Russian efforts to build a political alliance with trump's campaign. Racking up convictions, sending former aides to jail. Most nonotably, Michael Cohen. The moment he pled guilty -- He's a weak and not very smart person. Nobody likes a rat. Nobody. Cohen pleaded guilty, now cooperating with the special counsel. The information I gave to them was credible and helpful. So you're done with the lying? I'm done with the lying. I'm done being loyal to president trump. Sentenced to three years, Cohen says trump directed him to I never directed him to do anything wrong. Whatever he did, he did on his own. He directed me to make the payments, to become involved in these matters. Including the one with Mcdougal, which was really between him and David pecker. I just reviewed the documents. And trump's former campaign manager, also a felon. I feel very badly for Paul manafort. But this has nothing to do with what they started out, looking for Russians involved in our campaign. There were none. Where is the collusion? ?????? Witch hunt. Witch hunt. No collusion. It's a witch hunt. A witch hunt. Where is the collusion? There has been no collusion. Fake news and the Russian witch hunt. He probably says it in his sleep. Witch hunt. I think he's kind of dealing with things -- it's like presidential whack a mole. He attacked. He tried to do everything possible to stop it. The president, defiant as he awaits Mueller's report. What's the latest on the probe? The good news is, it's almost over. And the bad news? It's almost over. Trump did get some good news this year. Negotiating a new trade deal with Mexico and Canada, a new supreme court justice, unemployment at a 50-year low. I love trump. The man is doing what we want. His early economic victories, stalled by a dipping stock market. Pipe bombs sent to the president's critics highlighted deep political divisions. Opponents blame a brash leader for a polarized nation. Welcome to our special coverage of the most consequential and dramatic congressional hearing of all time. I never sexually attacked Dr. Ford or anyone. Internment camps for children. What country is that? Build the wall! Build the wall! The long-promised wall -- Mexico will pay for the wall. A rallying cry for the base in a contentious midterm election. But the wall, still not built, and still not paid for by Mexico. I will take the mantle of shutting it down, and I'll shut it down for border security. Washington begins its government shutdown, funding for several key federal agencies just expired. Bracing for the power shift about to consume Washington. Poor trump. For the next two years, he'll be in subpoena hell. He'll open up his kfc bucket, no, subpoena. He's already doubling down for 2020. My new slogan, keep America great, because that's exactly where we're heading. If you think this was something, wait until you see next year. We're going to fight, and we're going to win, win, win, win.

This transcript has been automatically generated and may not be 100% accurate.