"This person appears to have followed the whistleblower protection laws and ought to be heard out and protected. We should always work to respect whistleblowers’ requests for confidentiality," Sen. Chuck Grassley, head of the powerful Senate Finance Committee, said in a statement.
The Iowa Republican did not mention Trump by name, but said, "No one should be making judgments or pronouncements without hearing from the whistleblower first and carefully following up on the facts. Uninformed speculation wielded by politicians or media commentators as a partisan weapon is counterproductive and doesn’t serve the country."
Trump and some of his allies, including Ohio Rep. Jim Jordan and South Carolina Sen. Lindsay Graham, have said the identity of the intelligence community whistleblower whose complaint sparked the House's impeachment inquiry into the president should be made public, even though it's protected under whistleblower laws that Grassley helped write.
"Like every American, I deserve to meet my accuser, especially when this accuser, the so-called 'Whistleblower,' represented a perfect conversation with a foreign leader in a totally inaccurate and fraudulent way," the president tweeted Sunday.
A call summary of the July phone conversation released by the White House, however, comported with the whistleblower's allegation that Trump pressed the Ukrainian president to have Trump rival Joe Biden investigated.
The whistleblower's lawyer, Andrew P. Bakaj, said Trump's comments "have heightened our concerns that our client's identity will be disclosed publicly and that, as a result, our client will be put in harm's way."
On Monday, Grassley and another Republican senator, Ron Johnson of Wisconsin, sent a letter to the inspector general of the intelligence community, Michael Atkinson, after a conservative media outlet reported that the whistleblower complaint process had been loosened right before the person came forward.
The report in the Federalist had claimed the intelligence community "secretly gutted" a requirement that a whistleblower has to have firsthand knowledge of the alleged wrongdoing. The Ukraine whistleblower's complaint is comprised of mostly information the person was told by other officials.
Trump seized on the report to allege he was being victimized by "the swamp."
In their letter to Atkinson, Grassley and Johnson said, “We are not aware of any federal law, regulation, or internal directive relating to whistleblowers that requires first-hand information in order for the complaint to be accepted as credible or receive legal protections," and asked if there had been a change in policy.
Atkinson's office issued a statement later Monday saying there is no requirement that a whistleblower have firsthand knowledge of wrongdoing. It also noted that the Ukraine whistleblower did indeed have "direct knowledge of certain alleged conduct."
In his statement Tuesday, Grassley also pushed back against what's become a GOP talking point — that the secondhand information the whistleblower offered should be discounted. Republicans, including Louisiana Sen. Bill Cassidy and Texas Sen. John Cornyn, have dismissed the complaint as "hearsay."
“When it comes to whether someone qualifies as a whistleblower, the distinctions being drawn between first- and second-hand knowledge aren’t legal ones. It’s just not part of whistleblower protection law or any agency policy. Complaints based on second-hand information should not be rejected out of hand, but they do require additional leg work to get at the facts and evaluate the claim’s credibility," Grassley wrote.
He also took a swipe at Democrats, charging they were rushing to impeach the president.
“As I said last week, inquiries that put impeachment first and facts last don’t weigh very credibly. Folks just ought to be responsible with their words,” he said.