1. Russian interference with US election.
3. Trump financial or other ties to Russia and whether Russia has some leverage over him.
I guess there's a 4th now. Trump Admin interference with FBI investigation. Nixonian cover-up at its best.
And I want to remind that the "smoking gun" in Watergate was Nixon's plan to have Vernon Walters of the CIA to tell Patrick Gray of the FBI to let go of the Watergate Burglary Investigation because of trumped up "National Security" concerns relating to Cuba and the Bay of Pigs (some of the Watergate Burglars had been involved in the Bay of Pigs Invasion). [To his credit, Walters did not convey the message.]
The "smoking gun" was also directly linked to the cash payments from Nixon campaign funds (which he knew about) to Watergate Burglars with the intent to buy their silence. The FBI was hot on this evidence and is something that anybody should understand is crooked in several different ways.
Roy Cohn of McCarthy "Red-Scare" fame was Donald Trump's lawyer as he started out and trained him well in dirty legal, financial, political, and self-promotion tricks. The evils of our history keep circling back. It is our civic responsibility to call them out and do what we can to stop them.