Despite his otherwise fervent support for President Donald Trump, Sen. Lindsey Graham on Wednesday became the president's loudest critic once again.
The South Carolina Republican tore into Trump after media outlets reported that the U.S. was planning to pull its troops out of Syria. The reports were confirmed soon after by the White House and the Pentagon — and by Trump, who in a celebratory tweet declared victory against ISIS in Syria.
Graham hammered Trump on Twitter and in an official statement from his office, as well as in remarks to reporters, where he said that Trump's decision could undo the progress made against the Islamic militant group.
"I'll have to say if Trump withdraws from Syria and they do come back, like I think they will, he'll be one of the reasons they came back," Graham said.
A U.S. official told Reuters that all State Department personnel in Syria will be evacuated from the country within 24 hours, and that all U.S. forces will depart once that final operation against ISIS has been completed. The troops are expected to be withdrawn within 60 to 100 days, the official told Reuters. The State Department did not comment when reached by CNBC.
Graham has become one of the president's closest allies and loudest defenders. The senator has been credited as the difference-maker in the confirmation of Trump's second Supreme Court Justice nominee, Brett Kavanaugh.
But Graham's remarks Wednesday offered the senior senator's second public break with Trump administration this month. In early December, Graham cut against the White House's position that no "direct evidence" connected the killing of journalist Jamal Khashoggi to Saudi Crown Prince Mohammed bin Salman. "There's not a smoking gun, there's a smoking saw," Graham said at the time.
On Wednesday, Graham said the decision to withdraw "would be a huge, Obama-like mistake," and that it "will also be viewed as a boost to ISIS desire to come back."
In a statement from his office, Graham said: "An American withdrawal at this time would be a big win for ISIS, Iran, Bashar al Assad of Syria, and Russia. I fear it will lead to devastating consequences for our nation, the region, and throughout the world."
Graham and other lawmakers also pushed back hard on Trump's assertion that ISIS's forces in Syria had been "defeated." That mission was "my only reason for being there," Trump said in the tweet.
"With all due respect," Graham responded, "ISIS is not defeated in Syria, Iraq, and after just returning from visiting there -- certainly not Afghanistan."
Rep. Adam Kinzinger, R-Ill., said Trump's declaration of victory "is simply not true."
White House press secretary Sarah Huckabee Sanders said in a statement that "the United States has defeated the territorial caliphate," but added that "these victories over ISIS in Syria do not signal the end of the Global Coalition or its campaign."
Trump has previously expressed a desire to withdraw the 2,000-or-so troops still in Syria. And not every Republican opposes the idea: Sen. Rand Paul, R-Ky., said he was "happy to see" Trump declare victory in the Wednesday morning tweet.
Still, many of that policy's harshest critics were in Trump's own party.
Sen. Marco Rubio, R-Fla., said Wednesday that withdrawal would be a "grave error" and a "bad idea" because it "potentially helps ISIS." The policy also "runs the risk of triggering a broader conflict that could pull the United States in, but most certainly will impact our close ally in the region, Israel," Rubio said.
Sen. Cory Gardner, R-Colo., tweeted that the move "will embolden bad actors" in the region." He urged Trump to work with Congress on a long-term strategy that "denies a win for Vladimir Putin, Bashar al-Assad, and the Iranian mullahs."
Graham, speaking to reporters, said the move makes the United States "dramatically less safe."
"ISIS would not be alive today if it were not for Obama's decision to withdraw from Iraq. And I'll have to say if Trump withdraws from Syria and they do come back, like I think they will, he'll be one of the reasons they came back," Graham said. "So yes, this makes us less safe if there it's a fact a withdrawal."