Sen. Jeff Flake, R-Arizona, is expected to rebuke President Trump on the Senate floor Wednesday, in a speech that draws a comparison between Mr. Trump and Soviet dictator Joseph Stalin. In an excerpt of the speech obtained by CBS News' Alan He, Flake plans to call out Mr. Trump's repeated attacks on the news media, saying it's an "assault as unprecedented as it is unwarranted."

"Mr. President, it is a testament to the condition of our democracy that our own President uses words infamously spoken by Josef Stalin to describe his enemies," reads the excerpt. "It bears noting that so fraught with malice was the phrase 'enemy of the people,' that even Nikita Khrushchev forbade its use, telling the Soviet Communist Party that the phrase had been introduced by Stalin for the purpose of 'annihilating such individuals' who disagreed with the supreme leader."

"When a figure in power reflexively calls any press that doesn't suit him 'fake news,' it is that person who should be the figure of suspicion, not the press," he's also expected to say.

Get Breaking News Delivered to Your Inbox

Flake, a frequent critic of the president, penned an op-ed in the Washington Post in the fall, the day after he announced he would not seek re-election in 2018.

In a piece headlined "Enough," Flake compared the political climate to that of the McCarthy era in the 1950s, applauding the efforts of Joseph Welch, chief counsel for the Army at the time of the Army-McCarthy hearings, who delivered a stunning rebuke to McCarthy. He asked the senator, "Have you no sense of decency, sir, at long last? Have you left no sense of decency?"

"The moral power of Welch's words ended McCarthy's rampage on American values, and effectively his career as well," wrote Flake. "Welch reawakened the conscience of the country. The moment was a shock to the system, a powerful dose of cure for an American democracy that was questioning its values during a time of global tumult and threat. We had temporarily forgotten who we were supposed to be."

Flake referred to political discord being sowed in the era of Mr. Trump, a "sickness in our system -- and it is contagious."

Besides longtime target CNN, the president has picked fights with outlets like the "failing" New York Times and the Wall Street Journal, despite giving interviews with the news organizations. The Journal most recently found itself at the center of a Twitter spat with Mr. Trump over how he characterized his relationship with North Korean dictator Kim Jong Un. It quoted him as saying, "'I have a good relationship with Kim Jong Un." Mr. Trump and the White House maintain that he said, "I'd have a good relationship with Kim Jong Un. Both the White House and the Journal have released audio recordings to support their assertions.

The Wall Street Journal stated falsely that I said to them “I have a good relationship with Kim Jong Un” (of N. Korea). Obviously I didn’t say that. I said “I’d have a good relationship with Kim Jong Un,” a big difference. Fortunately we now record conversations with reporters... — Donald J. Trump (@realDonaldTrump) January 14, 2018

The Republican senator's remarks will fall on the same day the president is set to announce his picks for the "dishonest" and "corrupt" media of the year.

According to the president, subjects will cover "dishonesty & bad reporting in various categories from the Fake News Media."