Five possible successors to Mattis

President TrumpDonald John TrumpHarris bashes Kavanaugh's 'sham' nomination process, calls for his impeachment after sexual misconduct allegation Celebrating 'Hispanic Heritage Month' in the Age of Trump Let's not play Charlie Brown to Iran's Lucy MORE may find it difficult to replace Defense Secretary James MattisJames Norman MattisTrump needs a national security adviser who 'speaks softly' US could deploy 150 troops to Syria: report Trump blasts 'Mr. Tough Guy' Bolton: 'He made some very big mistakes' MORE following the Pentagon chief’s resignation this past week.

Mattis, who resigned Thursday after major policy disagreements with his commander in chief, enjoyed broad bipartisan support and the respect of U.S. allies, and for almost two years was able to weather a chaotic administration that has seen an unprecedented amount of Cabinet turnover.

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As Trump now looks to replace the former four-star general by the end of February, several names have emerged as possible front-runners.

But with few prospects who see eye to eye with the president and could garner sufficient support in the Senate, Trump’s top choice is anyone’s guess at this point.

“You got to find people who are willing to do it, and I think a lot of people are upset with [the Syria] call and also the second call where he’s talking about downgrading the Afghan numbers,” Senate Armed Services Committee Chairman James InhofeJames (Jim) Mountain InhofeIs the Senate ready to protect American interests in space? Republicans grumble over Trump shifting military funds to wall Gun debate to shape 2020 races MORE (R-Okla.) said, referring to Trump’s decision to withdraw U.S. troops from Syria and his consideration of halving the number of troops in Afghanistan.

Here are five potential candidates to succeed Mattis:

Former Sen. Kelly AyotteKelly Ann AyotteGOP fears Trump backlash in suburbs Trump makes rare trip to Clinton state, hoping to win back New Hampshire Key endorsements: A who's who in early states MORE (R-N.H.)

Sources close to the administration mentioned Ayotte as a possible Mattis successor. She was among those considered for the position before Mattis was nominated for the post.

The former New Hampshire senator has a strong defense background, having served as chairwoman of the Senate Armed Services readiness subcommittee while in Congress.

She lost her reelection bid in 2016, but before that was an outspoken GOP opponent of the 2015 Iran nuclear deal. She has also called for tighter sanctions on Iran and North Korea.

Not long after leaving the Senate, Ayotte served as the sherpa on Capitol Hill for Trump’s first Supreme Court nominee, Neil Gorsuch. Her name was also mentioned for other administration posts, including FBI director after Trump fired James ComeyJames Brien ComeyHouse Democrats seeking Sessions's testimony in impeachment probe Justice OIG completes probe on FBI surveillance of ex-Trump campaign aide Aggrieved Trump rips Dems for 'sad' impeachment effort MORE in May 2017.

But some of Ayotte’s positions may put her at odds with Trump, including her views on a troop pullout in the Middle East.

Ayotte criticized former President Obama for withdrawing U.S. troops from Iraq in 2011, indicating she may feel the same about Trump’s desired troop pullout in Syria.

While in the Senate, she was known as one of the “three amigos” with the late Sen. John McCainJohn Sidney McCain The 13 Republicans needed to pass gun-control legislation Biden's debate performance renews questions of health At debate, Warren and Buttigieg tap idealism of Obama, FDR MORE (R-Ariz.), a frequent Trump antagonist, and Sen. Lindsey GrahamLindsey Olin GrahamBolton exit provokes questions about Trump shift on Iran The 13 Republicans needed to pass gun-control legislation Graham: US should consider strike on Iranian oil refineries after attack on Saudi Arabia MORE (R-S.C.), who has been sparring with Trump in recent days over Syria and Afghanistan but is otherwise a strong ally of the president.

Sen. Tom CottonThomas (Tom) Bryant Cotton2020 Democrats raise alarm about China's intellectual property theft Bolton returns to political group after exiting administration Meadows, Cotton introduce bill to prevent district judges from blocking federal policy changes MORE (R-Ark.)

Speculation has circulated for months that Cotton — a member of the Senate Armed Services and Intelligence committees — could be tapped for a top role at the Defense Department or the CIA.

Cotton did not respond to reporters who tried to ask him about the opening on Friday.

As a former Army officer and veteran of the Iraq and Afghanistan wars, Cotton has made a name for himself in the Senate as a combative defense hawk. He has also backed Trump on major policy moves against Iran.

But at 41 years old he would be one of the youngest Cabinet picks in recent memory.

He’s also had some missteps. It was Cotton who reportedly suggested H.R. McMaster to Trump as national security adviser after Michael Flynn resigned in February 2017.

McMaster, who reportedly was not on the president’s radar until Cotton’s suggestion, ultimately butted heads with Trump and his approach to Russia, Iran and North Korea and was dismissed in March.

Cotton also broke with Trump on the announcement of plans for drawdowns of U.S. forces in Syria and Afghanistan, issues that also led to Mattis’s resignation.

Andy Keiser, a principal at the lobbying firm Navigators Global who worked on the Trump transition team's national security section, said he was unsure what effect Cotton’s position on Syria would have on his chances for defense secretary.

“That’s a really hard one to gauge,” he said. “Nikki HaleyNimrata (Nikki) HaleyCan Carl DeMaio save the California GOP? Treasury: US deficit tops trillion in 11 months South Carolina GOP appears to violate own rules in canceling primary for Trump MORE was pretty critical of the president and she got [U.S. ambassador to the United Nations]. So hard to judge what importance they place on one comment or another. Being fair, I think Tom Cotton is seen pretty favorably inside the White House and has spoken quite favorably of the president 99 percent of the time. So I think he would be on the safe side of that ledger.”

But complicating matters is whether Cotton would leave a safe Senate seat for a Cabinet position, and whether Trump would draw from the Senate.

Former Treasury Department official David McCormick

McCormick was named as a possible Mattis replacement by The Washington Post in September, when speculation of a post-midterm Mattis departure first sprang up.

A West Point graduate, McCormick is a combat veteran of the first Gulf War. During the George W. Bush administration, he served as under Treasury secretary for international affairs after stints as under secretary of Commerce for industry and security and deputy national security adviser for international economic policy.

He is now co-CEO of the world’s largest hedge fund, Bridgewater Associates, and is engaged to Dina Powell, Trump’s former deputy national security adviser for strategy.

He is said to run in the same social circles as Ivanka TrumpIvana (Ivanka) Marie Trump2020 is not a family affair, for a change Katy Tur says it is 'shameful' that Congress hasn't passed new family leave law OPIC should strengthen US-Argentine partnership with Vaca Muerta deal MORE and Jared KushnerJared Corey KushnerThe Hill's Morning Report - 2020 Democrats set for Lone Star showdown Exclusive: Kushner tells GOP it needs to unify behind immigration plan Arrests at southern border drop to 64K in August MORE, the president’s daughter and son-in-law, who both serve as senior White House advisers.

In 2017, though, he reportedly turned down an offer to be deputy Defense secretary because he was happy at his job at Bridgewater and did not feel that role was the right fit for him.

Deputy Defense Secretary Patrick Shanahan

Trump has settled on deputies before when he couldn’t find a replacement for a Cabinet head, and that could work to former Boeing executive Patrick Shanahan’s advantage.

The Pentagon’s second-highest-ranking civilian has an extensive corporate background, having started at Boeing in 1986, and was the senior vice president of the company’s supply chain and operations before he was tapped for the administration post in early 2017.

What’s more, Shanahan has taken on the role of reforming the Pentagon in its business and administrative practices rather than focusing or advising on war-fighting policy.

Shanahan has not only backed up Trump’s plans for a separate Space Force military service, he also leads the project within the Pentagon, frequently visiting the president and Vice President Pence at the White House.

He was not known to be close with Mattis.

Former Sen. Jim Talent (R-Mo.)

Shortly after the 2016 election, Trump’s transition team made a push for Talent to serve as Pentagon chief. The former Missouri senator, who previously served on the Armed Services Committee and maintains strong ties to Capitol Hill, even met with Trump in New York. And unlike many other Republicans in 2015 and 2016, he did not criticize Trump during the campaign

While in the running for Defense secretary, Talent was pushed largely by then-incoming White House chief of staff Reince PriebusReinhold (Reince) Richard PriebusPoliticon announces lineup including Comey, Hannity, Priebus Sunday shows - White House stresses Trump's determination in China trade fight as GOP challenger emerges Priebus: Left's 'wacko ideas' are opportunity for Republicans in 2020 MORE. But Priebus left the White House in July 2017, and it’s unclear if Talent has an influential West Wing supporter in his corner this time around.

Talent currently serves on the U.S.-China Economic and Security Review Commission, and he was appointed to the position by Senate Majority Leader Mitch McConnellAddison (Mitch) Mitchell McConnellO'Rourke responds to Buttigieg's gun criticism: 'That calculation and fear is what got us here in the first place' Cicilline on Trump investigations versus legislation: 'We have to do both' The 13 Republicans needed to pass gun-control legislation MORE (R-Ky.) for a two-year term that expires at the end of 2019.

James Carafano, a defense policy analyst at the Heritage Foundation who served on Trump’s transition team, mentioned Talent, as well as Sen. Jon Kyl (R-Ariz.), when asked who he thinks would make a good replacement.

“Somebody like a Jon Kyl or a Jim Talent — an experienced, respected senator that has real chops in terms of knowing national security issues, that people really respect that have been in the trenches in the Congress — somebody like that would be great,” he said. 

Talent was GOP presidential nominee Mitt RomneyWillard (Mitt) Mitt Romney The 13 Republicans needed to pass gun-control legislation Bolton returns to political group after exiting administration 2020 is not a family affair, for a change MORE’s top pick for Defense secretary in 2012.