We won’t learn anything new from former Ambassador to Ukraine Marie Yovanovitch’s testimony. That’s because she, like the two witnesses that testified before her, has no direct knowledge of alleged wrongdoing by the president, and anything she does know is based on hearsay.

Rep. Jim Jordan was the first to make that criticism in Wednesday’s impeachment hearing, which featured acting Ambassador to Ukraine William Taylor and Deputy Assistant Secretary of State George Kent, and he was right to do so. But Congress’s hands are tied: Every witness that might have first-hand knowledge of President Trump’s motivations and actions has been blocked from testifying by the White House.

It’s not surprising the White House would want to keep several of the key witnesses, including acting chief of staff Mick Mulvaney and former national security adviser John Bolton, from appearing before Congress. Any good lawyer would advise as much. But the White House needs to come up with better reasons for doing so.

White House counsel Pat Cipollone said in a letter to House Democrats last month that because the accusations against the president are based on “falsehoods and misinformation,” the White House does not need to cooperate.

The Democrats’ impeachment efforts are clearly partisan, and the White House is not legally required to comply, but the administration’s refusal could backfire. Impeachment is, after all, a process dependent on public opinion. If the public concludes that Trump has something to hide, he could be in trouble.

Trump has said multiple times that his July 25 phone call with Ukrainian President Volodymyr Zelensky was “perfect.” If that’s the case, what is there to hide? It could be that the White House isn’t hiding anything, and this is an attempt to limit its liability. If that’s true, Trump should stop talking about impeachment altogether — on Twitter and to the press. But he hasn’t, which contributes to the perception that the White House’s refusal to work with Congress isn’t about limiting inadvertent implications but covering Trump’s tracks.

Friday's hearing won't yield much because Yovanovitch’s testimony is irrelevant to the Democrats’ main charge against Trump. It’s unlikely the eight other witnesses Democrats have scheduled will have much more to offer.

Yovanovitch’s sudden removal was certainly imprudent and injurious, but it wasn’t impeachable — and the Democrats know it. Unless Congress hears from the White House’s first-hand witnesses, Democrats will be left grasping for straws.