What did Trump know, and when did he know it?

For one former federal prosecutor, the stakes are clear for Trump’s presidency if it’s discovered his campaign helped Russian operatives disseminate stolen Democratic emails during the 2016 campaign.

If Trump’s guilty, his presidency is over.

“He’s going down,” Paul Butler, former federal prosecutor and legal analyst, told MSNBC’s Chris Hayes, noting Trump would be guilty of a conspiracy crime if he acted in concert with the Russians during the election.

Special counsel Robert Mueller has recently been zeroing in on that crucial question, according to a Wednesday report from NBC News.

Investigators are “asking witnesses pointed questions about whether Donald Trump was aware that Democratic emails had been stolen before that was publicly known, and whether he was involved in their strategic release,” according to the report.

That kind of hands-on coordination would be the smoking gun that could end it all for Trump, said Butler.

“If the president was being more or less passive and understanding that the Russians have this information, this dirt on Hillary, and it would be really cool of it came out, but I don’t have anything to do with it. Then I don’t think he’s going to be the subject of an indictment or a report to congress recommending impeachment,” Butler said on MSNBC.

“On the other hand, if he was active in any kind of participation, any kind of active coordination about when the emails would be released … then he’s going down.”

On the same MSNBC program, former Watergate prosecutor Nick Ackerman stressed, “What we’re dealing with here is a conspiracy to break into the Democratic National Committee, steal emails, and use those emails to help Trump get elected, and the quid-pro-quo for that was the dropping of [Russian] sanctions.”

U.S. intelligence agencies concluded that Russians were behind the cyber heist of the Democratic emails in 2016. Russians are also suspected of delivering the emails to Wikileaks, the Trump-loving site that created political havoc for Democratic nominee Hillary Clinton during the campaign.

Mueller’s team is trying to determine whether the Trump campaign knew about the Russians’ role in the email hacking back in 2016, and if they helped the Russians disseminate the information.

Recall in June 2016, a publicist with Russian ties, in an email to the Trump team, offered up damaging information about Clinton as “part of Russia and it’s government’s support for Mr. Trump.” To which Donald Trump Jr. responded, “If it’s what you say I love it.” Trump Jr. then included the campaign chairman and Trump’s son-in-law to hear about the Clinton dirt and and about Russian sanctions.

When the meeting was disclosed in 2017, Trump Sr. helped concoct a phony cover story that the meeting had been about Russian adoption policy.

Also, during a press conference on July 27, 2016, just days after Wikileaks began publishing the internal Democratic communications, Trump openly mocked the situation. “Russia, if you’re listening, I hope you’re able to find the 30,000 emails that are missing,” Trump said.

Trump’s mantra is “No collusion.” Mueller will soon find out.