The more experienced democratic leaders like Sanders and Pelosi are saying it's too early to demand impeachment charges.
That's smart for a number of political and practical reasons:
1. The Mueller investigation is a still an ongoing investigation. So far 5 have pleaded guilty with 19 other formal indictments.
Nobody knows for sure, what (if any) criminal and /or conspiracy charges will be made against Pres. Trump.
Before anyone declares Trump as guilty or innocent, let's wait for the investigation to conclude.
The five that were indicted had NOTHING to do with "Russian collusion" in the case of Flynn, he was coerced and blackmailed into his guilty plea to protect his son to not get dragged into it. If you kept up, you would know this
2. Should the dems win back the house of reps, they can bring charges of impeachment on Pres. Trump.
BUT, they first need to win back the majority of seats. THEN the investigation has to bring evidence of
serious crimes on the sitting President.
Even if charges are brought fwd by the house, they still have to convict Trump .
THAT requires 67 senators to convict him with a guilty vote. Regardless of the 2018 midterms,
the dems won't have anything close to 67 senators. While a few GOP senators might vote against Trump, most won't UNLESS
the charges are really bad.
Don't forget that Bill Clinton was impeached but they failed to convict him.
Impeach him for what?
3. Except for a small % of diehard liberals, most of the country doesn't want the President dragged thru the political mud.
Obviously, the citizens will demand it , if and only if the charges are serious enough to warrant it.
If congress wants to remove a President, they better have a damn good reason for doing it.
Conclusion - I would strongly urge everyone to wait for Mueller to conclude his investigation.
Trump and his supporters are screaming that it's a Witch-hunt with nothing to show .
Nobody knows that now and they'll look pretty stupid if the final evidence shows criminal conduct by Pres. Trump.
1. Mueller said Trump was not a criminal target. 2. Trump has turned over almost 1.2million requested documents if there was anything found the public HAS A RIGHT to know asap and since Mueller is leaking to the press, we would have known by now.
I'd say the exact same thing to dems who say Trump's guilty and needs to be impeached.
Again, we don't know that now. I was one of the few Hillary voters , that urged caution in
declaring victory before the election. You can look pretty dumb ,when you jump the gun. 
Let's show some self-control and wait for Mueller's final report and conclusions.
Bottomline, with all of the HARD EVIDENCE against Clinton, this investigation is 100% bullshit and after it's all said done, Trump and co should come after all involved including disgraced, Robert Mueller with both fucking barrels without letting up. After Rosenstien is gone, Trump should fire Sessions to hell and back.