With Jim Mattis abruptly stepping down as Secretary of Defense last night, the chattering classes are buzzing with speculation on who President Trump might pick to replace him.

A familiar name is said to be on the short list: Sen. Tom Cotton. Cotton, a rigid ideologue and unreconstructed neoconservative, might be on an odd fit in certain ways. Trump just got done bickering with Mattis over the president’s desire to withdraw U.S. troops from Syria. Cotton never met an intervention he didn’t like (George W. Bush “did largely have it right,” Cotton has opined; Trump has in recent years offered a different take). 

But Cotton’s bluster and martial nationalism might appeal to Trump’s temperament, and Cotton has worked hard to ingratiate himself with the praise-hungry president over the last few years.

Cotton, allergic to diplomacy of any kind, has already had influence with the president in junking the nuclear deal with Iran (Cotton famously organized an open letter to Iranian leaders in an attempt to undercut the U.S. government’s negotiations with Iran on the deal, threatening that a future Congress or president could revoke on whatever terms were reached).

Politico’s reading of the tea leaves included six choices Trump might look at; here’s their writeup on Cotton:

Cotton, a member of the Senate Armed Services and Intelligence committees, has developed a reputation as a top defense hawk in just four years in the chamber. A top critic of national security policies in the waning years of the Obama administration, the Arkansas Republican has since positioned himself as one of Trump’s top Senate backers.

The 41-year-old former Army officer, who served in Iraq and Afghanistan, has been mentioned as a possible pick for secretary of Defense or CIA director.

But he’s also one of the most conservative members of the Senate and has been unafraid to ruffle feathers among his colleagues, so Cotton could have a bumpy confirmation process. It’s also unclear if he’d abandon a safe red-state Senate seat for a Cabinet post.

The Atlantic also included Cotton on its shortlist of four possible names:

The Republican from Arkansas is a member of the Senate’s Intelligence and Armed Services Committees. Cotton, 41, is a veteran of the wars in Iraq and Afghanistan, and was previously floated as a possible CIA director to succeed Mike Pompeo when he moved on to become Trump’s secretary of state. (The job instead went to Gina Haspel.)

Cotton is one of Trump’s staunchest supporters in the Senate, and particularly shares the president’s judgment that Iran is the major malign actor in the Middle East. But on other crucial issues, such as the importance of U.S. alliances, the withdrawal from Syria, and the drawdown in Afghanistan, the senator’s views hew more closely to the mainstream. Indeed, he and Senator Lindsey Graham—another potential contender—signed a letter criticizing the Syria decision and urging Trump to reconsider.

Still, his support for Trump could mean a rough confirmation battle. It’s also unclear whether he’ll want to a leave a position of influence in the Senate for a job that can be thankless, managing an unpredictable president who often veers off the agreed consensus. Additionally, given the president’s legal troubles and an incoming Democratic-controlled House of Representatives with subpoena power, Trump might want to keep his most reliable congressional allies in Congress.