The House Managers have convinced all of the Republicans it's possible to convince

[StarfishSaver]

32. You're assuming they'd be cooperating witnesses

They would be hostile witnesses and it would be days, maybe weeks before they would actually testify. And the testimony could be very muddled and not produce the kind of information some people think it might.

And it would put the House managers - who have built a tremendous amount of public goodwill for the impeachment process and how they've conducted it, in the position of having to tussle and fight publicly with cagey politicians who don't intend to answer their questions or give them the information they want.

And it won't change a single vote for conviction.

I think the better course of action is to, at most, get sworn statements from the Secret Service, if possible (it may not be easy to do that quickly) and then call the vote - and let the various Senate and House committees of jurisdiction take over the investigations. THEY can drag Pence, et al in to testify, fight over subpoenas, and hammer them with well-prepared questions from all sides.

But at this point, I don't think the impeachment managers need to big themselves down into trying to present evidence that will be difficult to get and won't make a difference to the process they're responsible for.