President Trump’s personal feud with two Senate Republicans has ramifications for his goals on national security and foreign policy in the months ahead.

Trump needs Senate Armed Services Committee Chairman John McCain John Sidney McCainBiden's six best bets in 2016 Trump states Replacing Justice Ginsburg could depend on Arizona's next senator The Hill's Morning Report - Sponsored by Facebook - Washington on edge amid SCOTUS vacancy MORE (R-Ariz.) and Foreign Relations Committee Chairman Bob Corker Robert (Bob) Phillips CorkerHas Congress captured Russia policy? Tennessee primary battle turns nasty for Republicans Cheney clashes with Trump MORE (R-Tenn.) to confirm his nominees to crucial positions, defend his administration’s positions and pass key legislative priorities.

The president is embroiled in highly-public spats with both men, however, which could make things tricky.

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“The essence of governing in Washington is knowing how to make a deal with Congress,” said Danielle Pletka, senior vice president for foreign and defense policy studies at the American Enterprise Institute. “Whether they’re your adversaries or your allies, telling them they’re a bunch of schmucks is not the best way forward.”

Corker and McCain both complimented Trump on Monday for his speech laying out U.S. policy on Afghanistan.

But by Friday, the president was lashing out at Corker over the Tennessean's remarks last week that Trump has not yet demonstrated “the stability nor some of the competence” to be successful.

“Strange statement by Bob Corker considering that he is constantly asking me whether or not he should run again in ’18. Tennessee not happy!” Trump tweeted Friday morning.

Earlier in the week, he took a shot at McCain during a campaign rally in Phoenix, needling the senator over his vote against ObamaCare repeal without mentioning his name.

“One vote away! I will not mention any names. Very presidential, isn’t it?” Trump quipped in front of a cheering crowd of McCain’s constituents.

As Armed Services chairman, McCain will play a significant role in the debate over Afghanistan. Before Trump’s speech, he had criticized the administration, warning he would legislate strategy himself if the White House did not take action.

Outside observers said there is little for Trump to gain from fighting his own party’s committee chairmen.

“It’s so petty that I think it inevitably weakens his presidency writ large and it’s such a shame,” said Michael O’Hanlon, a senior fellow in foreign policy at the Brookings Institution who specializes in defense strategy and military use of force.

“He was having a good week with Afghanistan and then he went to Arizona and then he continued with this tirade,” O’Hanlon said, referring to the tweet about Corker.

Gordon Adams, who worked in Bill Clinton William (Bill) Jefferson ClintonGOP brushes back charges of hypocrisy in Supreme Court fight Battle lines drawn on precedent in Supreme Court fight Sunday shows - Ruth Bader Ginsburg's death dominates MORE’s White House, said tensions between and administration and committee chairman of the same party are hardly unprecedented.

What’s different, he said, is how personal Trump’s attacks are, and how ancillary they are to policy issues.

“These are peculiarly hostile and peculiarly self-inflicted,” said Adams, now a professor at American University. “These are fights that Trump doesn’t have to pick. They’re fights over trivia. They’re not fights about issues of grave consequence for the nation’s security.”

Fighting with Congress can weaken the president’s hand on foreign policy by making the White House “the laughing stock of the world,” he added.

That’s particularly true of insulting McCain who is arguably the most well-known and respected U.S. senator abroad.

“People overseas are saying, ‘John, what do you think? Is this guy crazy?’ And that can undercut the president,” Adams said.

Corker, meanwhile, is the gatekeeper for the many assistant secretaries of State and ambassadors awaiting confirmation or yet-to-be nominated. Corker would also loom large over any treaties that need Senate approval.

Adams said he expects the administration’s plan to reorganize the State Department will need at least some legislation to actually happen, which would have to pass through Corker’s committee.

“There are whole areas that Corker can actually extract a price that are in the jurisdiction of his committee,” Adams said.

Corker is also a senator who had previously seemed to have a good relationship with Trump. He was considered to be in the running to serve as secretary of State.

The Tennessee senator spoke critically of Trump after the president lambasted Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellGraham: GOP will confirm Trump's Supreme Court nominee before the election Trump puts Supreme Court fight at center of Ohio rally The Memo: Dems face balancing act on SCOTUS fight MORE (R-Ky.) and criticized Sen. Jeff Flake Jeffrey (Jeff) Lane FlakeJeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Republican former Michigan governor says he's voting for Biden Maybe they just don't like cowboys: The president is successful, some just don't like his style MORE (R-Ariz.). Trump is also supporting a primary opponent of Flake’s next year.

Trump’s actions have been noted throughout the Senate GOP conference, hurting his relationships with Republicans.

A former Senate Republican aide who specializes in foreign policy said that frayed relationships with Corker and McCain could come back to haunt Trump should a national security crisis arise.

“As president, the last thing in the world he needs is hostile foreign policy Republicans making his life more difficult. At some point, it will matter,” the aide said.

The aide noted that some House Republicans voted to include an amendment in an appropriations bill that would have set up debate on the president’s use of military force in Afghanistan.

Trump will need allies on the Hill if the issue comes up again.

What confounds Republicans on Capitol Hill and defense experts alike is that Trump, McCain and Corker share many of the same defense and foreign policy goals.

“If he gets consumed by these sorts of things, it’s hard to see how anything good can come of it,” O’Hanlon said.

Trump may still be mad at Corker over his role in pushing Russia sanctions legislation, something that McCain supported as well.

He called Corker last month to personally vent his displeasure with the bill.

“Our relationship with Russia is at an all-time & very dangerous low. You can thank Congress, the same people that can’t even give us HCare!” Trump tweeted on Aug. 3.

Thomas Spoehr, a retired Army lieutenant general and director of the Center for National Defense at the conservative Heritage Foundation, said he thinks Trump’s criticism of McCain on issues unrelated to defense, such as healthcare, will not prevent the two from working together in areas of mutual interest.

For example, Spoehr cited McCain’s approval of the Afghanistan strategy Trump unveiled this week. He also said he thinks Trump will go along with McCain’s efforts to boost defense spending even beyond the administration’s budget proposal.

“I don’t think President Trump would disagree if [the defense budget] got a bit further than that and he could point that to as an accomplishment of his administration,” Spoehr said.

Still, because McCain is in control of the defense budget, it would be “wiser” for Trump not attack him, Spoehr acknowledged.

“You’d like to not see any unprovoked attacks,” Spoehr said. “I’d like to see the Republican Party a little more tightly focused. I’d like to see them less divisive, but we got what we got right now… I don’t care what they do behind closed doors, but if in public they could refrain, that’d probably be useful.”