President Obama is set nominate Jeh Johnson, his former general counsel at the Defense Department, to head the Department of Homeland Security, today. The department has been without a permanent leader since Janet Napolitano stepped down in August to head the University of California system.

Johnson's nomination "was not at all expected," says National Journal, noting that his name wasn't mentioned even once in its recent poll of "national security insiders." The appointment "comes as something of a surprise," says Daniel Klaidman at The Daily Beast, which first reported the news. But the White House hopes his "experience dealing with counterterrorism and cyber-security threats will comfort many on Capitol Hill."

While top lawyer at the Pentagon from 2009 until last December, Johnson (his first name is pronounced Jay) was a key player in formulating Obama's national security policies, notably those covering the lethal use of drones and changing the system for prosecuting terrorism suspects in military tribunals. He also led the departmental review that cleared the path for repealing the military's "don't ask, don't tell" policy on gays and lesbians serving openly in the armed forces.

Before that, Johnson, 56, was Air Force general counsel in the Clinton administration and an assistant U.S. attorney in New York City. When not serving in government, he worked at a white-shoe Manhattan law firm. He was also an early supporter and fundraiser for Obama's first presidential run in 2008.

Johnson's nomination requires Senate confirmation, and some Senate Republicans are already questioning whether a man who supervised 10,000 lawyers at the Pentagon is really prepared to take charge of 240,000 employees at the sprawling Homeland Security Department. It's a fair question. DHS, after all, deals with national security but also oversees FEMA disaster relief operations, the Secret Service, ICE, and the TSA.

To be fair, none of the other people rumored to be on Obama's shortlist — New York City Police Commissioner Ray Kelly, former Coast Guard Commandant Thad Allen, and TSA chief John Pistole — had experience in all those areas, either. Few, if any, people do. So it comes down to which facet of the Homeland Security Department the White House wants to emphasize. If Napolitano focused on the homeland part, Johnson will tackle the security half.

Johnson's nomination "suggests the agency will be stepping back from its preoccupation with immigration to focus more on protecting the nation from attack," says The Associated Press' Alicia A. Caldwell.

Napolitano, who came to the DHS after serving as governor of Arizona, made clear that her top priority was immigration reform and routinely championed the issue in congressional testimony. During her first hearing on Capitol Hill, she did not mention terrorism. That is unlikely to be the case with Johnson.... Two previous secretaries, Napolitano and Michael Chertoff, were also one-time federal prosecutors. But Johnson's national security and military experience may eclipse both of them. [AP]

Johnson faces some criticism on the right for his role in repealing DADT and for suggesting last December that U.S. operations against al Qaeda should be downgraded from war to law enforcement and intelligence gathering. Some commentators on the left also criticize Johnson for, as Bob Dreyfus at The Nation puts it, spending "years justifying War on Terror's excesses," notably by helping ramp up drone use and personally approving drone strikes.

Johnson's legacy is a little more complicated than that. He successfully pushed to move the CIA's drone program to the less-secretive Defense Department, and since leaving the Pentagon, Obama's "drone lawyer" has argued publicly that Obama should have a more transparent policy on when and how the U.S. authorizes drone strikes.

Johnson has his supporters, too. "He's really a good choice," former chief Guantanamo Bay military prosecutor Morris Davis tells Bloomberg News. "He was in my view the best general counsel we had in my 25 years in the Air Force. He's got the legal acumen, the people skills, the organizational skills."

And Johnson's boss at the Pentagon, former Defense Secretary Leon Panetta, says "Jeh worked on every major issue affecting America's security, including border security, counterterrorism, and cyber security," urging the Senate to "act quickly to confirm him."

And in the end, that's the constituency Johnson and his handlers have to win over: The Senate. The two senators most important to his nomination, Tom Carper (D-Del.) and Tom Coburn (R-Okla.), are somewhere between favorable and noncommittal. Carper, chairman of the Homeland Security committee, called his nomination "welcome news," while Coburn, the committee's top Republican, raised concern about wasteful spending; both said they looked forward to talking with him.