Initially, impeachment investigators were in negotiations to interview the whistle-blower, a C.I.A. officer who was detailed to work at the White House, in a way that would protect his identity. But eventually the claims in the complaint were supported by other direct evidence.
Some Republicans, including Mr. Trump, have demanded that the whistle-blower be revealed and questioned his motivations and the details of his complaint. As The Times’s Charlie Savage explains, while whistle-blowers are protected from being fired or demoted, they are given only a limited right to anonymity, and Mr. Trump and his allies are not barred from unmasking him if they learn who he is.
Is the impeachment process preventing Congress from getting other things done?
It’s only a part of it. In the words of Carl Hulse, The Times’s chief Washington correspondent: “While impeachment roars on, everything else is kind of stuck.” But it has more to do with polarization and divided government than the impeachment process itself.
Republicans control the executive branch and the Senate, while Democrats control the House. There are issues waiting for a vote — a looming government shutdown and President Trump’s new North American trade agreement — but the House committees’ work on impeachment is far from the only thing behind the holdup.
The Evidence
Adam B. Schiff, Democrat of California and the Intelligence Committee chairman, summarized six weeks of testimony like this:
“President Trump conditioned official acts — a White House meeting desperately desired by the new Ukrainian president and critical U.S. military assistance — on Ukraine announcing sham, politically motivated investigations that would help President Trump’s 2020 re-election campaign.”
As Mr. Schiff’s staff works to compile a report making their case for impeachment, House Republicans are working on their own report to counter the Democrats’ conclusions.
Is key evidence secondhand or thirdhand?
Yes, some of the testimony is based on information that was relayed to witnesses by other people. Republicans undercut some of the first testimony as hearsay, but as other witnesses began to corroborate accounts, they began to back away from that strategy.
Many firsthand witnesses, including John Bolton, Mr. Trump’s former national security adviser, and Mick Mulvaney, the acting White House chief of staff, have defied subpoenas and requests to testify.