Donald Trump Donald John TrumpBarr criticizes DOJ in speech declaring all agency power 'is invested in the attorney general' Military leaders asked about using heat ray on protesters outside White House: report Powell warns failure to reach COVID-19 deal could 'scar and damage' economy MORE and John McCain John Sidney McCainKelly's lead widens to 10 points in Arizona Senate race: poll COVID response shows a way forward on private gun sale checks Trump pulls into must-win Arizona trailing in polls MORE wrote a new chapter in their long feud this week, when the president ripped the Arizona GOP senator for emboldening the enemy by calling last month’s U.S. raid in Yemen a failure.

The nasty jousting between a Republican president and senator was both unusual and predictable.

The two have repeatedly clashed on personal terms. One of Trump’s first controversies was to mock McCain’s time as a prison of war, saying he liked people “who weren’t captured.”

McCain has repeatedly criticized Trump on foreign policy, knocking him for being too willing to give Russian President Vladimir Putin the benefit of the doubt and criticizing his attacks on a Gold Star family during the presidential campaign. He was one of a number of Republicans who stayed away from the GOP convention.

ADVERTISEMENT

At the same time, McCain has also played the part of dutiful Republican. He has voted for every Trump Cabinet pick, and he played down any animosity with Trump after the business mogul won the GOP presidential nomination.

Trump is likely to need McCain’s help in advancing his agenda.

The 2008 GOP presidential candidate is the chairman of the Senate Armed Services Committee and will play a huge role in Defense policy over the next two years.

McCain could foil Trump in policy areas such as torture and Ukraine through the annual defense authorization bill.

He’s warned Trump not to lift sanctions against Russia, which have been imposed over Moscow’s annexation of Crimea; its backing of separatists elsewhere in eastern Ukraine and its meddling in the U.S. election.

In that vein, McCain recently teamed up with five other senators from both parties on a bill that would require congressional oversight before Trump can lift the sanctions.

The fight between McCain and Trump this week was over the raid in Yemen, which left one Navy SEAL and a number of civilians dead.

The White House has insisted the operation was a success, with spokesman Sean Spicer saying anyone critical of it was doing a disservice to the fallen SEAL.

Hours later, McCain told NBC News that it’s fair to criticize a mission for failing and still hold respect for those who serve, noting his feelings about a failed mission to save him from a prisoner of war camp in Vietnam.

It all might have ended there, were it not for the president’s fondness for Twitter.

“Sen. McCain should not be talking about the success or failure of a mission to the media. Only emboldens the enemy! He's been losing so long he doesn’t know how to win anymore,” Trump tweeted Thursday.

Trump’s tweet made more headlines, though McCain didn’t take the bait and refused to offer another comment — but he did tweak the president again on Russia.

In an interview this week, Trump said the U.S. is not innocent in response to a comment about Russian President Vladimir Putin being a killer.

McCain said he “strongly disagrees” with the president on Putin.

“What we need to do is understand Vladimir Putin for what he is -- a murderer and a thug,” McCain told reporters.

Supporters of McCain shrug off his criticisms of Trump, arguing they are no different from his public criticisms of President George W. Bush and President Obama.

After Bush beat him in the 2000 primary, McCain was sometimes a thorn in the side of the new president. And after Obama defeated McCain in 2008, the Republican was often seen as one of the new president’s most strident critics. Some even wondered if bitterness over the defeat played a role in McCain’s criticism at the time.

Former aides say McCain has been consistent throughout his career.

“What you are seeing is John McCain being John McCain. This is no different than when George W. Bush was president, when Barack Obama Barack Hussein ObamaGOP senator blocks Schumer resolution aimed at Biden probe as tensions run high D-Day for Trump: September 29 Obama says making a voting plan is part of 'how to quarantine successfully' MORE was president, and now when Donald Trump is president,” one former McCain aide told The Hill.

“He says what he believes, whether it’s in support of the president or not. That’s been a hallmark of his entire career.”

Further fights between McCain and Trump seem almost certain.

Neither likes to back down from a fight, and it is hard to believe that Trump’s criticisms of McCain haven’t got under his skin.

They have certainly irritated his family members.

Meghan McCain, the senator’s daughter, lashed out at Trump this week, nothing that her father, grandfather and brothers had all served in the military while Trump had not.

“McCain is very proud of his ‘maverick’ brand and Donald Trump is who he is. So I don’t think the two will ever be close,” one Trump ally outside of the White House said.

Gordon Adams, a professor at American University who worked on defense budgeting in the Clinton administration, called McCain and Trump’s fight over the Yemen raid a “microcosm” of what’s to come in the next few years.

While the National Defense Authorization Act isn’t a typical vehicle for sanctions legislation, Adams said he wouldn’t be surprised to see language in this year’s tying Trump’s hands on Russia sanctions.

“The old phrase about Congress is that they go along to get along -- not in John McCain’s case,” Adams said.