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's (R-Ariz.) former adviser, Richard Fontaine, said on Monday that he fears the late senator may have been the last politician willing to take risks in the political arena.

"I hope not, but I worry that he might be," Fontaine told Hill.TV's Krystal Ball and Ned Ryun on "Rising," when asked if he thinks McCain was the last politician willing to set aside their own political interests for the good of the country.

"There are other senators and politicians on the national scene who I think could step up in major ways, and who do things here and there across party lines, and on matters of principle and things like that," he continued.

"One of the things in addition to acting on principle that was always important to Sen. McCain was unifying the country, working across party lines to try to strike deals, and build political support among both Republicans and Democrats," he said.

"Today I think we have a president, and we have most members of Congress who are not terribly interested in unity. They're interested more in polarization."

McCain often broke with the GOP during his tenure in the Senate, opposing the Bush tax cuts and recently opposing efforts to repeal and replace ObamaCare.

Republican and Democratic lawmakers from across the country paid their respects to McCain after he died on Saturday, a year after being diagnosed with brain cancer.

— Julia Manchester