So here's the thing: neither the Constitution nor any Federal law defines, "high crimes & misdemeanors." So it is literally up to the House of Representatives to decide what that expression means in any given case. It doesn't have to be a legal crime, and there is no need for "proof beyond a reasonable doubt." It could be a breach of protocol, or something that simply makes the U.S. look bad.
And if the House of Representatives decides that Trump asking the President of Ukraine to do some "Oppo Research" for him, and implicitly threatens to withhold some financial aid if the President of Ukraine declines to cooperate, constitutes HC&M, then that's it. It does. You'll get no argument from me - an ardent Trump supporter - on that.
But if you insist on asking, "What law was broken," it's surely true that the army of Leftist lawyers out there can dredge up some law from 1493 that appears to be relevant, but this is all bullshit. No real, current, meaningful law was broken. That is why they are talking about him "violating his oath of office." Which Congress has the legitimate power to deem a "high crime and misdemeanor. But one might further ask, "Do the people get a vote on this?"
Yes.
Because with everything that has been done to this President, based on NOTHING but Democrat and Deep State outrage that he won the 2016 Presidential election, the People might be inclined to say, "This goes too far." And, for example, the People in my personal Congressional district, who elected Democrat Conor Lamb last time...if HE were to vote to impeach on this this thin pretense of a "crime," he would be voted out of office, provided a credible Republican were to get in the race.
So Nancy P has a bit of a problem. Her caucus is still infested with a significant number of Democrats who won in "swing" districts, and THOSE Democrats won't vote to impeach unless the President has committed a REAL crime, not some bullshit breach of polite political practice.