(CBS NEWS) -- Sen. Jeff Flake, R-Ariz., delivered a pointed message to President Trump in an op-ed in the Washington Post on Wednesday, the day after he rattled the political world by announcing he would not seek re-election in 2018.

In a piece headlined "Enough," Flake compares 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, asking 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."

The Republican writes that the country faces similar times today, saying that "we have again forgotten who we are 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."

The senator points to Mr. Trump's recent controversy surrounding his contacts with Gold Star families and what he calls the president's "childish insults" being hurled at a "hostile foreign power," likely referring to Mr. Trump's tweets at North Korean dictator Kim Jong Un.

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