WASHINGTON (AP) — President Barack Obama’s choice to lead the Transportation Security Administration withdrew his name Wednesday, a setback for an administration still trying to explain how a man could attempt to blow up a commercial airliner on Christmas Day.

Erroll Southers said he was pulling out because his nomination had become a lightning rod for those with a political agenda. Obama had tapped Southers, a top official with the Los Angeles Airport Police Department, to lead the TSA in September, but his confirmation has been blocked by Republican Sen. Jim DeMint, who says he was worried that Southers would allow TSA employees to have collective bargaining rights.

In an e-mail to friends and colleagues, Southers said, “It is unfortunate that we are residing in such contentious political times, that exceptional, ‘apolitical’ candidates have to seriously consider their willingness to participate in public service.”

Questions have also been raised about a reprimand that Southers received for running background checks on his then-estranged wife’s boyfriend two decades ago. Southers, a former FBI agent, wrote a letter to lawmakers earlier this month acknowledging that he had given inconsistent answers to Congress on that issue.

In an October affidavit for the Senate Homeland Security committee, Southers initially said he asked a San Diego police employee to run a background check on his then-estranged wife’s boyfriend and was censured by his FBI superiors 20 years ago for what he said was an isolated instance.

But a day after the committee approved his nomination and sent it to the full Senate, he wrote to the senators and told them that he was incorrect, that he had twice run background checks himself.

DeMint said in a statement that the White House never responded to requests for more information relating to the incident. He said he hoped the president would quickly choose a new nominee.

The White House said Wednesday that Obama had accepted Southers’ withdrawal with great sadness and continued to believe he would have made an excellent TSA administrator.

The withdrawal of Southers’ nomination was another setback for the TSA at a time when the government is still trying to answer questions from Congress about how a man was able to carry out a bombing attempt on Christmas Day on a Northwest Airlines flight from Amsterdam to Detroit.

Democrats had lined up behind Southers’ nomination after the December incident, with Majority Leader Harry Reid, D-Nev., saying he would call for a full Senate vote on his confirmation this year.

The administration has been beset by problems with intelligence and security nominees. It took Obama eight months to nominate people to lead TSA and Customs and Border Protection – two key security agencies that play large roles in preventing another terrorist attack like the attempted Christmas bombing that shook the nation and the governmental establishment.

Senate Democrats also have accused Republicans of stalling the nomination of Caryn Wagner, the administration’s nominee to be the top intelligence official at the Homeland Security Department. In June, Obama’s initial pick for intelligence chief at Homeland Security withdrew his nomination amid questions about his role in the CIA’s interrogations of suspected terrorists.

The inability to analyze disparate pieces of information has been at the core of the failure to stop the Christmas Day attempted attack.

Associated Press writer Eileen Sullivan contributed to this report.

Photo: Erroll Southers