Sen. Johnny Isakson Johnny IsaksonLobbying world Loeffler paints herself as 'more conservative than Attila the Hun' in new campaign ad Georgia GOP Senate candidates cite abortion in pushing Ginsburg replacement MORE (R-Ga.) on Monday warned President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE or any other critics against speaking negatively about GOP Sen. John McCain John Sidney McCainAnalysis: Biden victory, Democratic sweep would bring biggest boost to economy The Memo: Trump's strengths complicate election picture Mark Kelly: Arizona Senate race winner should be sworn in 'promptly' MORE (Ariz.) as the nation mourns his death this week.

"I don't know what's going to be said in the next few days about John McCain ... but anybody who in any way tarnishes the reputation of John McCain deserves a whipping, because most of the ones who would do the wrong thing about John McCain didn't have the guts to do the right thing when it was their turn," Isakson said from the Senate floor.

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He added that he would convey "to the president or anybody in the world, it's time to pause and say this was a great man. He gave everything for us. We owe him nothing less than the respect that he earned."

Isakson's speech came as Trump has faced backlash over his handling of McCain's death. He sent a tweet on Saturday expressing sympathy for McCain's family but reportedly nixed releasing a statement that called the 81-year-old former GOP presidential nominee a "hero."

Trump appeared to reverse course on Monday afternoon. The White House released a statement from Trump expressing "respect" for McCain despite their political differences.

Trump also ordered flags to fly at half-staff after being criticized when he returned them to full staff less than 48 hours after McCain’s death.

Trump and McCain had frequently criticized each other, going back to the first days of the president's White House campaign. Trump had recently taken to mocking McCain at campaign rallies for his thumbs-down "no" vote on ObamaCare repeal, and McCain denounced as "disgraceful" Trump's widely derided press conference with Russian President Vladimir Putin.