"McCain, who was the party's nominee himself in 2008, has long been comfortable on the bad side of presidents. The Armed Services Committee chairman trashed George W. Bush's tenure over his handling of the Gulf War and the mounting national debt and constantly accused President Barack Obama of weak leadership abroad.
"I'm the one that said Ronald Reagan shouldn't send Marines to Afghanistan," McCain told CNN in early February. "I'm the one that said Donald Rumsfeld should be fired. I've said the general in Afghanistan should be fired. Look, I have done what I have done right for this country under Republican and Democrat presidents. I will continue to do so. This is not a departure from the way I've conducted myself in the United States Senate."
Trump made clear he viewed McCain as an opponent in 2015, when he belittled the senator's five years as a prisoner of war in Vietnam by questioning McCain's "war hero" status, saying, "I like people who don't get captured."