The fact that both involved elections is a telling similarity, showing the insecurity of both Nixon and Trump that they needed to go outside normal channels, they could not win.  We all know that Russian hackers were involved with the leaks and likely the Russian government.  It was no secret.  Trump may have won anyway, although the last Comey leak was an undeserved gift.  Still, Hillary did not pick up the "only for Obama" vote which put him over the top.  Corey Booker as VP might have given it to her but she did not go that way and probably did not consider that she should.

Will Trump be impeached?  After 2018, former Speaker Pelosi will likely get her old job back, but she refused to impeach Bush, or even Cheney (who deserved it and worse) because she would not criminalize bad government.  Trump's current incompetence is not criminal, just difficult to watch. He is more likely out if  Pence and the Cabinet believe him emotionally disabled, which is where my money is.