FACTBOX: Napolitano in the spotlight since Detroit incident

(Reuters) - U.S. Homeland Security Secretary Janet Napolitano has been the prime political target for critics who say a failed Christmas Day airplane bombing attempt should have been prevented and the Obama administration's response was too slow and inadequate.

Republicans argue that President Barack Obama and his Democrats are soft on battling Islamic extremists. Napolitano has been criticized for first saying the air security system had worked during the Christmas Day incident aboard a U.S.-bound plane and then backtracking by saying she meant the system of beefing up measures worked after the incident.

Here are five facts about Napolitano:

* The 52-year-old Democrat had law enforcement experience before joining Obama's cabinet, as a former U.S. attorney for Arizona and state attorney general. But she was widely seen as having been picked for the Homeland Security post because she had been closely involved in immigration issues as governor of Arizona, a state bordering Mexico.

* Napolitano became nationally prominent in 1991, when she was an attorney representing law professor Anita Hill, who charged Clarence Thomas with sexual harassment during the Senate Judiciary Committee's hearings on his nomination to the Supreme Court by then-President George Bush, a Republican. Napolitano's role in that case helped spur Senate Republicans to hold up her nomination for more than a year when Democratic President Bill Clinton tipped her as U.S. Attorney for Arizona in 1993.

* Napolitano is the third person, and the first woman, to be head of the sprawling Homeland Security department, which Republican President George W. Bush formed to bolster civil defense after the September 11, 2001, attacks.

* Although Arizona politics are dominated by Republicans, Napolitano, a Democrat, was popular there. She was narrowly elected in 2002 for her first term as governor but won a landslide victory in 2006. However, she issued more vetoes than any other Arizona governor, with both houses of the state legislature controlled by Republicans.

* There has been widespread speculation that Obama might nominate Napolitano for the Supreme Court, amid talk that 89-year-old Justice John Paul Stevens will retire in 2010.

(Compiled and written by Patricia Zengerle, editing by Paul Simao)