The Homeland Security Department's responsibilities include routine immigration issues, cybersecurity, protecting the president and keeping would-be terrorists off airplanes. The DHS also includes the Coast Guard.
Tom Ridge, the first DHS secretary and a former Pennsylvania governor, said this week that whoever takes over the department should be expert in a few of the department's missions, but not all. He said understanding national security is paramount.
"We need someone who appreciates that you can't secure the country from inside the Beltway," said Ridge, who has been critical of some of Obama's national security strategies.