Ashton Carter emerges as top pick for Defense. Why Obama might want a wonk.

The Oxford University-educated theoretical physicist has a reputation for getting things done and is well-regarded by Republicans, particularly Sen. John McCain.

After a number of prominent candidates dropped out of the running for secretary of Defense, Ashton Carter has emerged from the Beltway rumor mill as the White House’s choice for the job, a not-so-flashy pick that highlights President Obama’s desire for a known quantity with a reputation for getting things done. Dr. Carter is widely regarded as a stable numbers guru who has demonstrated enduring compassion for US troops.

The Pentagon, for its part, is keeping mum.

“I’m obviously mindful of the swirl out there,” Rear Adm. John Kirby, Pentagon press secretary, said in a briefing Tuesday afternoon. “This is a decision that only the president can make, and only the president can announce.” 

He added that the Pentagon had "no information about who the nominee might be, and when the nominee might be announced.”

Dr. Carter would be a popular pick with a number of Republicans, most notably Sen. John McCain (R) of Arizona, the new chairman of the Senate Armed Services Committee – an important consideration for a White House bracing for a tough confirmation hearing that will no doubt turn into a referendum on the Obama administration’s policies in the Middle East and elsewhere.

Carter is “a very good man,” Senator McCain told Fox News.

“I think he’s been very good on defense acquisition and some other programs,” he added. “I just hope that he realizes that if he takes the job, he will not have influence, just as his three predecessors didn’t, on national security policy. As long as he understands that, then so be it.”

Carter served as deputy secretary of Defense – the Pentagon’s No. 2 job – from 2011 to 2013. With a doctorate in theoretical physics from Oxford University, Carter has long specialized in the complex world of military procurement. When he was undersecretary of Defense for Acquisition from 2009 to 2011, for example, it was his job to sign off on the billions in new weapons and technology that the building buys each year.

Former Defense Secretary Leon Panetta writes in his new memoir that he elevated Carter to be his deputy in part because he admired the way in which Carter helped Panetta’s predecessor, Robert Gates, rapidly field mine-resistant vehicles in Iraq and Afghanistan by “smashing some old bureaucratic totems. That’s no small feat,” Mr. Panetta wrote, adding that Carter is also “the rare leader who understood both the policy and budget sides of the agency.”

“He’s a wonk, a nuclear physicist and author, but he’s also a compassionate commander who would slip out on weekends to visit wounded soldiers at Bethesda and Walter Reed” medical centers, Panetta added.

Mr. Gates, for his part, recalls that when he established a task force to tackle roadside bombs in 2009, he asked Mr. Carter to head it up and get the equipment there with all due haste. Carter “seized the opportunity with real passion,” he wrote in his 2014 memoir. “Others, however, still needed to have a fire lit under them.”

Carter even helped to develop a plan to disrupt the fertilizer supply chain, making it more difficult for insurgents to obtain bomb-making ingredients, Gates notes.

Carter has also demonstrated a willingness to play hardball. When the ever-embattled F-35 Joint Strike Fighter jet was over budget and under-performing, Carter developed a plan for Gates that included withholding a considerable $614 million in performance fees from Lockheed Martin and firing the two-star general who was the program manager. 

“I accepted all his recommendations,” Gates writes.