Trump's criticism of the late senator and war hero came after senior Republican lawmakers offered implicit and explicit criticism of the President for remarks earlier this week attacking McCain.
Senate Veterans' Affairs Chairman Johnny Isakson called Trump's attacks "deplorable" in an interview with Georgia Public Broadcasting's "Political Rewind" radio programme .
"That's what I called it from the floor of the Senate seven months ago," Isakson said, when the senator criticised the Trump Administration for lowering the White House flag to half-staff for only a single day following McCain's death. "It will be deplorable seven months from now if he says it again and I will continue to speak out."
The flag was returned to half-staff following Isakson's criticism.
Trump recalled the controversy over McCain's memorial services during his remarks today, claiming that he "gave him the kind of funeral he wanted" but "didn't get a thank you". McCain lay in state at the US Capitol - a decision made by congressional leaders, not Trump - before his burial last year.
Other Republican senators also weighed in on Trump's fresh attacks on McCain, the former Armed Services Committee chairman. McCain, an Arizona Republican who had served in Congress since 1983, was a one-time Navy pilot who was North Vietnam's most prominent prisoner of war.
Senate Majority Leader Mitch McConnell praised McCain in a tweet today that didn't mention the President or his criticisms. McConnell of Kentucky wrote that he missed McCain every day and added, "It was a blessing to serve alongside a rare patriot and genuine American hero in the Senate."
Senator Mitt Romney of Utah, who was just elected to a six-year term, said on Twitter, "I can't understand why the President would, once again, disparage a man as exemplary as my friend John McCain."
Senator Lindsey Graham, long McCain's best friend in the Senate, tweeted praise for McCain without mentioning Trump. Graham of South Carolina has become perhaps Trump's most important ally in the Senate, changing his tune dramatically from before Trump's election when the senator predicted that he would destroy the Republican Party.
Most Republicans go to great lengths to avoid criticising Trump, to keep from also becoming targets of a presidential tirade on Twitter. Trump remains immensely popular among Republican voters, which makes such a move especially risky. Former senators Jeff Flake of Arizona and Bob Corker of Tennessee both tussled with Trump and retired rather than face tough Republican primary challenges in 2018.
Isakson of Georgia is somewhat insulated from political pressure because he won his third Senate term in 2016 and won't be up for re-election until 2022. Still, he needs Trump for issues important to his state, such as a disaster-relief package scheduled to be on the Senate floor next week.
"We're all Americans," Isakson said on the radio programme. "There aren't Democratic casualties and Republican casualties on the battlefield, there are American casualties, and we should never reduce the service that people give to this country."
Trump as a candidate in 2015 picked a fight with McCain, declaring that the Navy veteran was "not a war hero" for spending five years being tortured in a Vietnamese prison and refusing advantages offered to him because his father was a prominent military leader. "I like people who weren't captured," Trump said at the time.
Senate Democratic leader Chuck Schumer said on Twitter he will re-introduce his legislation to rename the Russell Senate Office Building after McCain, whom he called an "American hero." The building was named in 1972 after Georgia Democratic Senator Richard Russell, a proponent of racial segregation who fought the Civil Rights Act.
Isakson rejected Schumer's call to rename the Russell building, saying Schumer is "just playing politics."
- Bloomberg