CNN's John Berman discussed the beginning of tomorrow's impeachment hearings with Sen. Chris Murphy.

"How will you watch tomorrow? What is your checklist? What are you looking for?" he said.

"Well, I think we already know what happened so this story has already become clear. The president of the United States wanted Ukraine to help him destroy his political rivals, and in exchange he would give them security aid or access to the white House," Murphy said.

'That is absolutely unallowable in a democracy, and so i guess what I'm looking for is that the witnesses this week are simply going to confirm the testimony they have already given to the impeachment inquiry committee. I don't think there's actually probably going to be a lot of drama this week. For the first time Americans will see Bill Taylor and others in person and I think what they will see are patriots, are career public servants who have really no reason to tell this story other than their desire to get the truth out.

"But I'm not sure we're going to see any bombshells. I think we already know what happened. I think we already know that it is something that is unacceptable in a country that governs itself by the rule of law, and it's really more of a question about what we're going to do about it, what the House is going to do and what the Senate's going to do."

Berman asked how Murphy thought they could make the case for impeachment.

"Well, ultimately we'll have to wait in the Senate for the articles of impeachment to arrive before we make a decision as to whether this is impeachable conduct. I've made it pretty clear that if you allow for a president of the United States to use the massive power that is given to him or her in their office to try to advance their own personal interests or their financial interests, then we really aren't a democracy any longer. We look much more like a tin pot dictatorship. I think we've got to make it clear to the American people if you allow this to happen without any consequence then you're basically setting up every future president to be able to use taxpayer dollars as leverage to try to get themselves reelected. and we just can't allow that to become precedent in this country."