[Street Pharmacist]

What's lost in this is that Trump didn't do anything illegal. He could walk up to Comey and say "I command you to stop investigating Flynn because you'll find something I don't want" and it's not illegal. He has the constitutional authority to do that. Only Congress can find him guilty of "high crimes and treason", and that could be jaywalking if Congress deems it so.

The legal definition of obstruction isn't as important as the political one: will there be enough in the testimony to convince Republicans that if they don't act their seats are at risk? It's the electorate that will decide this.

We keep hearing that it does or doesn't constitute obstruction of Justice depending on who's telling the story. It's all irrelevant because it's the American people who will decide that by forcing the Republican's hand. They have a lot at stake because their legacy will be attached to him for years after he leaves regardless of impeachment or finishing the eight years. If they agree to impeach, they'll suffer ramifications. If they wait and he turns out around even slightly, they may be better off and can maybe make some policy in the meantime.

As you can see, all of this is a set of political calculation. None of it is legally defined, so the simple answer is that impeachment is only the outcome when the Republican's see their future better with Trump impeached. I think the special election in Georgia 6 (deep red seat that's currently a toss up) will scare them more than Comey.