Sen. Rand Paul (R-Ky.) on Monday demanded the media reveal the identity of the anonymous whistleblower who raised concerns about President Trump's contacts with Ukraine, leading to the House's impeachment inquiry.

Paul, speaking in his home state at a Trump campaign rally, referenced unconfirmed reports in conservative media that the whistleblower worked for former Vice President Joe Biden, questioning the person's credibility.

"We also now know the name of the whistleblower. The whistleblower needs to come forward as a material witness because he worked for Joe Biden at the same time Hunter Biden was getting money from corrupt oligarchs," Paul said at the rally after Trump invited him onstage.

"I say tonight to the media, do your job and print his name," Paul told the crowd to loud cheers.

The whistleblower is subject to federal protections against retaliation under the law; his attorneys have been negotiating with Congress about an agreement for possible testimony that would protect the individual's identity.

In a statement to The Hill, Mark Zaid, the whistleblower's attorney, suggested Paul was "betray[ing] the interests of the Constitution and the American people" by calling for the whistleblower to be unmasked.

"A member of Congress who calls for the identity of any lawful whistleblower to be publicly revealed against their wishes disgraces the office they hold and betrays the interests of the Constitution and the American people," Zaid said.

Paul encouraged Republicans in Congress to more vociferously defend Trump against House Democrats' fast-moving impeachment inquiry, which is centered on a July 25 phone call in which Trump asked Ukraine's president to investigate Joe Biden and his son Hunter Biden's business dealings in Ukraine.

The call triggered an extraordinary intelligence community whistleblower complaint alleging Trump used his office to solicit foreign interference in the 2020 election, in which Joe Biden is a leading Democratic candidate. Trump has denied doing anything improper on the call, describing it as "perfect."

Trump and his Republican allies such as Paul have sought to undercut the whistleblower's credibility as closed-door hearings have produced damaging testimony about Trump and his administration's actions with respect to Ukraine.

Paul took aim at Hunter Biden on Monday evening, claiming he engaged in corruption by landing business deals overseas while his father was vice president. There is no evidence either Biden engaged in criminal wrongdoing.

"President Trump has great courage. He faces down the fake media everyday," Paul said at the outset of his remarks. "But Congress needs to step up to have equal courage to defend the president."

Trump, who introduced Paul as a "warrior" and a "great friend," was impressed by his remarks, telling the crowd after Paul concluded, "Wow, that was excellent. Wow, thank you."

Earlier Monday, Trump himself called for the whistleblower to testify publicly, saying written answers to lawmakers' questions were "not acceptable."

Trump was in Kentucky promoting the reelection of Gov. Matt Bevin (R), one of three governors facing an off-year Election Day on Tuesday, along with those of Mississippi and Virginia.