I'm trying to think about the purpose of calling the whistleblower. What would be the questions?
"Did you hear directly the President ask the Ukraine to investigate Hunter Biden in exchange for releasing the funds?"
"No, Coln Vindman told me he did."
"Oh, so you have nothing to add to this?"
"No, I have nothing to add beyond what Coln Vindman has already testified to. I will just reiterate that Coln Vindman told me that the President was asking Ukraine to investigate Hunter Biden in exchange for releasing the funds."
"Objection, your honor! The witness is providing hearsay."
"Sustained. The witness will only provide information that he has direct knowledge of."
"Sorry, your honor. I cannot testify to having heard directly the President's request. For that information, you need to ask Coln. Vindman."
GOTCHA! Huh?
Redirect:
"Mr. Whistleblower, would you say that Coln Vindman's testimony agrees with what he told you, and is the information upon which you provided your report?"
"Well that, and the information I got from XXX and information I heard directly."
"Your honor, we would like to call XXX to the stand."
If the complaint is that the whistleblower relied on hearsay information in filing the report, then his (or her) testimony is not admissible, right? And the case cannot depend on the information provided in the whistleblower report.
Then again, as far as I know, no part of the case as coming out so far relies on the information in the whistle blower report.