WASHINGTON (AP) — President-elect Donald Trump’s choice for defense secretary, Pete Hegseth, is heading into a potentially explosive Senate confirmation hearing

The hearing at the Senate Armed Services Committee is the start of a weeklong marathon as senators begin scrutinizing Trump’s choices for more than a dozen top administrative positions. The Republican-led Senate is rushing to have some of Trump’s picks ready to be confirmed as soon as Inauguration Day, Jan. 20, despite potential opposition to some from both sides of the aisle.

He is among the most endangered of Trump’s Cabinet choices, but GOP allies are determined to turn Hegseth into a cause célèbre for Trump’s governing approach amid the nation’s culture wars. Outside groups, including those aligned with the Heritage Foundation, are running costly campaigns to prop up Hegseth’s bid.

Hegseth, 44, attended Princeton University and served in the Army National Guard from 2002 to 2021, deploying to Iraq in 2005 and Afghanistan in 2011 and earning two Bronze Stars. But he lacks senior military and national security experience.

The secretary’s main job is to make sure the U.S. military is ready, trained and equipped to meet any call to duty. But the secretary also must ensure that American troops are safe and secure at home, with proper housing, health care, pay and support for programs dealing with suicide, sexual assault and financial scams.

Besides being a key national security adviser to the president, the defense secretary oversees a massive organization, with nearly 2.1 million service members, about 780,000 civilians and a budget of roughly $850 billion.