Sen. Jeff Flake (R-Ariz.) renewed his challenge to President Trump with a long speech on Wednesday that drew parallels between Trump’s verbal assaults on the media and terms used by one of the most notorious dictators of the 20th century.

Flake, a frequent Trump critic who has decided to retire rather than seek reelection this year, compared the president’s use of words such as “enemy of the American people” to the “enemy of the people” phrase that Russian dictator Joseph Stalin used against his critics during his reign of terror.

“Of course, the president has it precisely backward,” Flake said. “Despotism is the enemy of the people. The free press is the despot’s enemy, which makes the free press the guardian of democracy.”

The senator was delivering the first of what he has said would be several speeches about Trump’s presidency, taking aim at both the president’s assault on some of the societal norms that protect democracy and his Republican colleagues for not standing up to Trump.

“Our own president uses words infamously spoken by Joseph Stalin to describe his enemies,” Flake said, before noting that that should be “the source of great shame for us in this body, especially for those of us in the president’s party.”

“They are shameful, repulsive statements,” he said of Trump’s words.

White House press secretary Sarah Huckabee Sanders said she found the criticism odd since Flake himself had recently “defended a repressive regime.” She was referring to Flake’s contention earlier this month that U.S. investigators have not found proof that American diplomats were attacked by an unknown weapon while serving in Cuba.

“He’s criticizing the president because he has terrible poll numbers,” Sanders said, adding that Flake is seeking “some attention.”

Flake’s speech, given around the same time as a news conference at which House Speaker Paul D. Ryan (R-Wis.) tried to make the case for the GOP plan for funding the government for the next month, was aired live Wednesday morning on two cable news network, MSNBC and CNN.

Few senators were on hand for Flake’s speech, unlike when he stunned his colleagues in October by announcing his plan to retire at the end of his term. He acknowledged then that his party had turned sharply to the right and made it impossible for him to win the Republican nomination to seek another term unless he toed the line on Trump’s actions.

Sen. John McCain (R-Ariz.), who is home battling an aggressive brain cancer, joined Flake’s cause with an op-ed in The Washington Post that expressed some of the same criticisms against the president.

“Trump continues his unrelenting attacks on the integrity of American journalists and news outlets. This has provided cover for repressive regimes to follow suit,” McCain wrote.