THE TIGHTENING NOOSE:

Trump abruptly withheld nearly $400 million in military aid sometime in early July, and word spread through the administration in subsequent weeks. Though several witnesses told lawmakers that Ukrainians likely didn't discover the hold until late August -- after a POLITICO report revealed it -- Cooper said she began to register concerns days or weeks earlier.

Some, she said, arose from the defense industry that was awaiting the distribution of funds -- including at least one call Cooper received from the Chamber of Commerce.

"So before the kind of press broke on it, we were hearing that there were signs of concern," Cooper said.

But it was a conversation Cooper had with Volker that led her to believe Ukrainians also knew about the hold on aid before it was reported.

"I knew from my Kurt Volker conversation and also from sort of the alarm bells that were coming from Ambassador [William] Taylor and his team that there were Ukrainians who knew about this," Cooper said.

Cooper said Volker relayed to her a discussion with a top aide to Ukrainian President Volodymyr Zelensky about the Ukrainian leader making a statement alluding to "election interference" that Ukraine had committed in the past -- a nod to Trump's demand for such an investigation.

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