"Fox & Friends" host Brian Kilmeade said Tuesday that President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE's approval would get "extremely formidable" heading into 2020 because critical GOP senators such as the late Sen. John McCain John Sidney McCainCindy McCain endorses Biden: He's only candidate 'who stands up for our values' Biden says Cindy McCain will endorse him Biden's six best bets in 2016 Trump states MORE (Ariz.) are "basically gone."

"In terms of [Trump's] approval rating, it’s around 43 percent," Kilmeade said on "Fox & Friends," before predicting that Trump's popularity could shoot up after the full report from special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE's Russia investigation is released.

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Kilmeade added that “barring anything unforeseeable," Trump's support would be solid heading into the 2020 election.

“He will be extremely formidable going in because the Jeff Flakes and the John McCains, and sadly in John McCain’s case, that are pushing against the president, basically are gone," Kilmeade said.

Flake, a former GOP senator from Arizona, did not run for reelection last year and was a repeated critic of Trump's. McCain, who spoke out against Trump's rhetoric and policies many times, died of brain cancer last August.

The comments from Kilmeade came just weeks after Trump renewed his attacks against the late senator. Trump went after McCain several times in late March, calling his 2017 vote against repealing ObamaCare “disgraceful” and saying that he would "never" be a fan.

He also spent about five minutes slamming McCain while talking to workers at a tank factory in Lima, Ohio.

"I gave him the kind of funeral that he wanted, which as president I had to approve. I don’t care about this. I didn't get 'thank you.' That's OK," Trump said at one point. "We sent him on the way, but I wasn’t a fan of John McCain."

Kilmeade said at the time that Trump's attacks against McCain were uncalled for.

“The problem is he swapped his own message by going after George Conway George Thomas ConwayGeorge and Kellyanne Conway honor Ginsburg Lincoln Project releases new ad blasting Trump as 'a horrible role model' George Conway hits Trump on 9/11 anniversary: 'The greatest threat to the safety and security of Americans' MORE and in that speech inexplicably segueing to go after John McCain,” Kilmeade said on "Fox & Friends" the day after the speech. “It makes absolutely no sense.”