So far, no mainstream news organization has named the individual. Donald Trump Jr. linked on Twitter to an article in Breitbart, a far-right website, which cited another conservative news outlet that purported to name the person. Trump Jr. denied coordinating with the White House, and the name has not been confirmed.
Sen. Rand Paul (R-Ky.), who appeared with Trump at a rally Monday in Lexington, Ky., urged media to out the whistleblower, declining to do so himself. "Do your job and print his name," he said.
On Wednesday, Paul blocked a Senate resolution that would have reaffirmed support for whistleblower protections, prompting an exchange with the bill's sponsor, Sen. Mazie Hirono, a Hawaii Democrat.
"Let's be clear. The real purpose of these attacks is to scare anyone else who may be thinking of coming forward to stay silent," Hirono said on the Senate floor.
Transcripts from closed-door impeachment hearings released this week show that Republican attorneys have asked questions in several hearings intended to reveal or confirm the person's identity. None of the witnesses did so.
Republicans have also sought to force the whistleblower to testify in Congress, rejecting Zaid's offer to have his client answer their written questions.
"All whistleblowers are not created equal," Sen. Ron Johnson (R-Wis.) said Thursday on Fox News. He called the whistleblower an "anonymous informant" and said "it was pretty unreasonable for the whistleblower to expect to remain anonymous."
Trump has claimed that the whistleblower gave false information in a complaint that alleged Trump pressured Ukrainian President Volodymyr Zelensky to investigate Democrats, including former Vice President Joe Biden, after freezing nearly $400 million in U.S. aid to Ukraine.
But a memorandum of the call, released by the White House, and testimony by multiple witnesses have borne out the whistleblower's narrative. Three witnesses are scheduled to testify next week in the first public hearings of the impeachment inquiry.
The current circumstances do not directly echo Plame's. But there are similarities.