DW: Why is the indictment and arrest of longtime Donald Trump adviser Roger Stone so significant?

Richard Painter: This is direct evidence of collusion between high-ranking officials in the Trump campaign and WikiLeaks to obtain documents stolen by the Russians in the 2016 election. There is other evidence, of course, of collusion between the Trump campaign and the Russians. So this clearly closes the loop and makes clear that the Trump campaign was colluding with the Russians, with WikiLeaks to obtain damaging emails that have been stolen from Hillary Clinton and the DNC.

While President Trump is not directly implicated in this new indictment, do you think he could be in the future?

Absolutely yes, the president and high-ranking officials in the campaign, including perhaps even, or probably, Jared Kushner and Donald Trump Jr, who were in the Trump Tower meeting with the Russians to talk about incriminating dirt on Hillary that they wanted to get. So this is all starting to come together. This is a very bad situation for President Trump.

Read more: Trump ally Stone arrested for lying to Russia probe

The indictment states that "a senior Trump Campaign official was directed to contact Stone about any additional releases and what other damaging information Organization I had regarding the Clinton Campaign." Who could this senior Trump campaign official be?

We don't know. There is some speculation that it was Steve Bannon, but we simply don't know at this point. Steve Bannon was very much tied in to Cambridge Analytica and various other groups that use technology to conduct campaign activities in the election. But we just don't know at this point.

Would you say this is most significant indictment so far?  

It is certainly one of the most significant. Remember we already have President Trump's campaign manager Paul Manafort indicted, charged, convicted. We have Rick Gates, the deputy campaign manager indicted, charged, convicted. We have got his lawyer Michael Cohen, who has been arrested, charged, and pled guilty. And we have got various other officials close to President Trump who already have been found guilty of serious criminal activity. But this one is definitely very, very significant.

What does this now mean for President Trump himself and how dangerous is this for him and his campaign?

It is very dangerous for the United States, because as the prosecutors move closer and closer to Donald Trump and senior members of his campaign — including his own family — we are very concerned that his irrational behavior is going to increase. And that is a dangerous situation when he is in control of nuclear weapons and has as much power as he does.

You said that the Stone indictment proves collusion and closes the loop. What then do you expect as the next step in the Mueller investigation?

I would expect that the person on the other end of this conversation, the senior official of the Trump campaign, will be indicted because it is clearly a conspiracy between the two of them. So I would expect that step to happen, probably soon. And then we have the other officials in the Trump campaign and President Trump himself, who has engaged in obstruction of justice all along.

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You were counsel to President George W. Bush. If you were counsel to President Trump, what would you tell him now?

He ought to be talking to his own personal lawyer. I was the official White House ethics lawyer for President Bush. But at this point President Trump ought to talk to his own personal lawyer because he and members of his family have very substantial exposure to criminal charges.

And I have said before: I think this is just that much more evidence that he does need to work an agreement with the prosecutors. The federal prosecutors and the State of New York prosecutors are all looking at him and his family; he needs to work on an agreement and probably resign the presidency in return for some leniency. I think we would be much better off if he negotiated a plea agreement.

Read more: Cohen plea signals 'blockbuster indictment,' says Watergate prosecutor

Finally, it is important to note that the Stone indictment is just that: an indictment and not conviction by a court. So if you look at this indictment and the evidence that the Mueller team has presented, how credible is it?  

It looks very convincing. The Mueller team has moved very deliberately, some would say too slowly, but when they indict, they want to make absolutely sure they have got what they need to win the case. And they have had a very, very good track record obtaining guilty pleas and convictions in these cases. And I would expect that they would not have brought this case if they did not have overwhelmingly powerful evidence.

Richard Painter served as the chief White House ethics lawyer for President George W. Bush from 2005 to 2007. He is a law professor at the University of Minnesota and a board member of the legal watchdog group Citizens for Responsibility and Ethics in Washington (CREW).