What is going on with Lindsey Graham?

At one time, he viewed Trump as "unfit for office." Now, he appears to be Trump's biggest fan.

Chairman Sen. Lindsey Graham, R-S.C., appears as Facebook's General Counsel Colin Stretch, Twitter's Acting General Counsel Sean Edgett, and Google's Law Enforcement and Information Security Director Richard Salgado, testify during a Senate Committee on the Judiciary, Subcommittee on Crime and Terrorism hearing on Capitol Hill in Washington, Tuesday, Oct. 31, 2017, on more signs from tech companies of Russian election activity. (AP Photo/Andrew Harnik)
Chairman Sen. Lindsey Graham, R-S.C., appears as Facebook's General Counsel Colin Stretch, Twitter's Acting General Counsel Sean Edgett, and Google's Law Enforcement and Information Security Director Richard Salgado, testify during a Senate Committee on the Judiciary, Subcommittee on Crime and Terrorism hearing on Capitol Hill in Washington, Tuesday, Oct. 31, 2017, on more signs from tech companies of Russian election activity. (AP Photo/Andrew Harnik)

Onetime Trump critic Sen. Lindsey Graham (R-SC) has apparently become the president’s biggest cheerleader.

Two years ago this week, Graham urged the Republican party to tell then-candidate Donald Trump to “go to Hell.”

“You know how you make America great again? Tell Donald Trump to go to hell,” Graham said on CNN in December 2015.

In February 2016, Graham appeared on Fox News and called Trump a “kook.”

“I think he’s a kook. I think he’s crazy. I think he’s unfit for office,” Graham said. “I’m a Republican, and he’s not. He’s not a conservative Republican, he’s an opportunist. He’s not fit to be president of the United States.”

At the time, Graham, fresh off his own failed presidential bid, was one of the loudest voices in the “Never Trump” camp. On Election Day last year, he proudly tweeted that he cast his vote for Evan McMullin, the Never-Trump darling who ran for president as an Independent, instead than Trump.

Trump, for his part, has come out against Graham over the past year as well, calling Graham a “lightweight” and a “little boy” who seems “not as bright as Rick Perry.”

These days, Graham is back on television, but he’s singing an entirely different tune.

“What concerns me about the American press is this endless, endless attempt to label the guy as some kind of kook not fit to be president,” Graham told CNN on November 30, echoing his own words from February 2016.

After a round of golf Sunday, Graham also tweeted a rousing endorsement of the Trump International Golf Course, disregarding the fact that his promotion of the president’s private business entity appeared to skirt ethics rules.

“Trump International Golf Club is a spectacular golf course,” he wrote. “Great day of fun playing with @POTUS @realDonaldTrump.”

Graham has gone to bat for the president in more questionable ways as well, as MSNBC notes, promoting conspiracy theories about Trump’s former campaign rival Hillary Clinton and urging the Senate Judiciary Committee to investigate “ALL THINGS 2016 — not just Trump and Russia.”

“Was there collusion between DOJ and Fusion GPS to use Democratic funded dossier for political and legal purposes? We need to know the answer to those questions,” he tweeted on December 8. “It’s long past time for a Special Counsel to investigate Clinton email scandal, Uranium One, role of Fusion GPS, and FBI and DOJ bias during 2016 campaign.”

Graham — who once pushed former director of national intelligence James Clapper to investigate Trump’s finances during a Senate Judiciary hearing — appears to have forgotten his previous criticisms of Trump altogether. Instead, he’s opted instead to play nice, actively promoting businesses from which the president still benefits, and using his own position of power to push largely debunked anti-Clinton conspiracies for Trump’s gain.

In many ways, Graham’s flip-flopping is much more sinister in nature than that of his colleagues, Sens. Bob Corker (R-TN) and Jeff Flake (R-AZ), who have both come under fire recently for criticizing Trump publicly. Both Corker’s and Flake’s sudden and aggressive condemnations of the president should be taken with a grain of salt, as they’re on their way out (Corker announced he would not seek re-election in September, and Flake did the same in October). Graham, by comparison, is still very much an active and leading voice in the U.S. Senate — one that has taken the unique step of defending a wildly controversial president who has a habit of skirting ethics laws himself.

At a time when politicians of all stripes are finally turning on Trump and seeing his actions for what they really are, Graham is doing the opposite, cozying up to a man he once believed to be unfit for the Oval Office in an effort to save his own political skin.