In fact, I'm pretty sure he doesn't know. The House has enough to draft and pass numerous articles of impeachment.

1. Trump violated the Hobbs Act. That's bribery & extortion. (Testimonies, texts, partial phone transcript, his speech on the South Lawn, timeline, etc.)

2. Trump is threatening the whistleblower. That's high crimes and misdemeanors.

3. According to Giuliani, Trump authorized a shadow diplomacy in the Ukraine. That's an abuse of power.

4. Obstruction. Trump is actively stonewalling a Congressional investigation.

I'm just going with the obvious. There are more that Congress can hit Trump with.

However, here's the thing: Congress is trying to get more information to convince the American people. That's why the impeachment inquiry will go on although Trump wants the testimony and collection of evidence to stop. He wants to be impeached NOW so the Senate dictates the information. Why the hell would the House do that?