Transcript for The year ahead in politics

Thank you, Eva. Now to a year ahead in the white house. That means a new congress, a new white house. That means Robert Mueller's investigation. My friend is there, senior congressional Mary Bruce, and Terry Moran. Happy new year, you guys. Happy new year. So Terry, any way you slice it this is going to be a huge year for Mueller. Reporter: This is really the showdown year, right? Between Donald Trump and Robert Mueller. It is a story that as you well know could consume this white house, this presidency. Or not because Robert Mueller because he has not leaked unlike other prosecutors. There is a lot of smoke there. What we'll learn is just what he has got, if anything, on the president of the United States, and then that key moment. What does Donald Trump do as that prosecutor comes closer if he does? Does he fire him? Does he plunge the country into a crisis that way? Right now it is a black box pretty much. We know there is smoke, smoke, smoke. Is there fire? That's not the only investigation, Mary. You have got your eye on the hill. They have got a ton of investigations they are potentially looking into. Reporter: Democrats now are in control of the house when they come back here later this week and that means they will be putting this white house, this administration under an intense microscope. They feel the president has been able to act unchecked so not only are they looking at what Robert Mueller is doing in the Russia investigation, but they are looking at his tax returns to conflicts of interest to possibly looking at the business dealings with his family. There is a really wide net that congress is casting here, and of course then, they can't just investigate. They know they also have to legislate and so you're going to see them take action. Likely first up is something to show that there is a new sheriff in town. They will be taking action to try to address corruption in Washington. They certainly know, especially Democrats are well aware, that Americans are fed up with this town and they want to send a message that they are here and they are setting a new tone. Are you telling me that 2019 is going to be just as 2018? I thought we were going to catch a break. I think it will be more busy. It may be more busy and that piece that's missing is the one that people want. What are they going to do together, right? This guy is a fighter. The Democrats are spoiling for a fight, but the country wants to see some kind of progress made, some actual deal, a I think they will get at message maybe on infrastructure, right? Maybe on the opiate crisis, the worst drug crisis in the history of the United States. Maybe they will do a deal. Terry, the optimist. There are areas for potential compromise, but Democrats are in charge of one chamber, and Republicans the other. There is still gridlock. 2019 is all about get ready 2020. The president is campaigning for a re-election. Democrats are throwing their name in the hat. You know, we have got potentials like Joe Biden, kamala Harris out of California. But for me, the question is will there be a Republican challenger in this? Do you care to take a guess? If there is a Republican challenger, they will not win. The Republican party is now the trump party and you can see in the midterms if trump comes Toure state, you have a much better chance of winning and the idea that someone would take him on and dislodge him from the Republican party, you would have to have a completely different world which Robert Mueller may create, or not. And there are so many people, especially up on the hill who are eyeing this part of town, right? Republicans included, maybe some who have recently retired or left the hill, but man, it's going to be a real uphill battle for any Republican. I think for the Democrats the question for them is do they want to fight and get down in the mud with trump or are they going to try what Beto O'rourke tried? There will be meditation tips later in the show. Stick around and watch. I need them. I know you do too. Happy new year again.

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