The White House quickly named R. David Paulison to succeed Brown on an acting basis. Paulison, a former firefighter, has been director of the agency's preparedness division for the past two years.
In contrast to Brown, who had relatively little experience dealing with disasters and emergency response before joining FEMA, Paulison has spent his career in the field, having been chief of the Miami-Dade Fire Rescue Department before joining the federal government in 2001 as administrator of the United States Fire Administration.
In an interview Monday night, Brown said that he felt that his role had become an obstacle to the agency's work.
Brown, 50, said he had felt no pressure to resign. He said he made his decision on Sunday with his family after a long conversation on Saturday night with Andrew H. Card Jr., the White House chief of staff.
Brown's departure was hardly surprising, given the decision, announced on Friday, to remove him from management of the federal response to Hurricane Katrina.
Brown had become a political liability to the White House, even in his constrained new role. Democrats in Congress had been questioning how the administration could retain him in such an important job as director of FEMA after his performance in responding to the hurricane.
A poll taken over the weekend by the Pew Research Center for the People and the Press, a nonpartisan research organization, found that more than 6 in 10 respondents judged the federal government's response to be fair or poor. A variety of polls in recent days have found Bush's approval ratings at or near their lows, with his support eroding even among Republicans.
