The Russia investigation is "expanding, both in size and scope," according to The Washington Post. But an investigation is very different from a conviction or let alone a prosecution. For that you need evidence, and now there might actually be some. Evidence for the Russia investigation is likely mounting and making Trump pretty uncomfortable if you believe what experts are saying about the impanelling of a grand jury. Figuring out what that evidence could be is a bit trickier, but there are some clues out there.
Ryan Lizza of The New Yorker explained one key thing about the grand jury: It cannot be used to investigate hunches or "hoaxes." It has to be used for a federal investigation based on something, fact or evidence. "It can’t be used for a fishing expedition," Matt Olsen, a former federal prosecutor, told Lizza. So Robert Mueller, the federal prosecutor heading up the Russia investigation, has likely found something.
The team investigating alongside Mueller are experts on "cybercrime, white-collar crime, the mob, money laundering, and Watergate," The Post explained. Right now they can use the grand jury to to subpoena witnesses and documents to try and explore the various potential ties Trump and his associates have Russia. First, they'll probably stick to the documents. And that may be some of the evidence they've collected so far, but that's just the beginning.
Trump Jr.'s Emails
One of the most obvious pieces of evidence could be the email chain between Donald Trump Jr. and his friend Rob Goldstone, a publicist who set up a meeting with a Russian lawyer. The emails literally promise information that "would incriminate Hillary and her dealings with Russia and would be very useful to your father." But that's not all. It continues, "This is obviously very high level and sensitive information but is part of Russia and its government’s support for Mr. Trump.”
Russians Talk Paul Manafort
CNN reported that U.S. intelligence agencies have supposedly intercepted communications hinting that Russians wanted to work with Paul Manafort, then the Trump campaign chairman, to coordinate attacks on Clinton's campaign. These recordings could be vitally important, though Manafort has firmly denied colluding with Russia. Documents surrounding his time working in Ukraine for a pro-Russia party could also grow to be of interest.
Trump Firing James Comey
There's talk from Vox that several FBI officials are prepared to testify about whether or not Trump obstructed justice when he fired former FBI director James Comey. Their testimony could be evidence, but so could Trump's letter in which he fires the former director, Comey's written memos on his meetings with the president, and the interview in which Trump insinuates to NBC that the Russia investigation played a role in his firing Comey.
Michael Flynn's Work History
Some of the first documents that the grand jury requested from the White House had to do with the former national security adviser. It seems their main interest is whether he secretly worked for Turkey during the final stages of the election. If there's proof that Flynn was receiving the foreign payments without being registered as a foreign agent, that would be a crime. Also, hiding the income could get him in hot water too.
Financial & Business Transactions
Financial transactions and business dealings are perhaps the biggest focus of the investigation at this point. That's because financial crimes are easier to prosecute, CNN reported. According to a report from the news outlet, all sorts of people and businesses tied to Trump, the Trump Organization, and the presidential campaign are being looked into. "They've combed through the list of shell companies and buyers of Trump-branded real estate properties and scrutinized the roster of tenants at Trump Tower reaching back more than a half-dozen years," CNN's report reads.
This last bit of potential evidence is what seems to upset Trump the most. In an interview with The New York Times in August, the president said that if Mueller starts investigating his business dealings, that would be a red line that should not be crossed. When specifically asked, Trump didn't say he would fire the special counsel if it happened. "I can’t, I can’t answer that question because I don’t think it’s going to happen," Trump said.
But if that's where the evidence is, you can be sure that Mueller is going for it. Just like he's shown with all these other areas of the investigation.