Quid pro Woah
Since the Mueller investigation didn't compel Congress to start impeachment proceedings Trump just went and engaged in more activity that is a minimum questionable. The current investigation that has the most traction of getting Trump to be impeached is his phone call with Ukrainian President Zelensky. He mentioned that Ukraine has military aid waiting to be paid out. Then there's a sudden shift to a favor: start back up the investigation in Vice President Biden and his son.
I believe I'm a reasonable person and I'd take that as a quid pro quo (this for that). There are people that don't believe that to be a quid pro quo and then there are other supporters of President Trump that say there is nothing wrong with the quid pro quo because we need to have Biden investigated.
To them that's not a high crime or misdemeanor. The Constitution is very clear on what a president can be impeached. The problem is there is no clear indication of what is a high crime or misdemeanor. So the Constitution goes further: treason and bribery.
Bribery: the receiving or offering any undue reward by or to any person whomsoever. The Federal Officer does not need to be the one receiving a bribe but the mere offer of a bribe constitutes a violation from what I read in the Constitution. A quid pro quo is a bribe. It's the same as if being pulled over I put a $100 bill on the dash of my car and ask the cop for a favor of giving me a warning. This for that is does not have to be overt it's implied with how close the subjects matter are being discussed.