Transportation Secretary Ray LaHood, a former Republican congressman who joined President Obama's Cabinet, said today he won't serve in the second term.

In an email to DOT employees across the country, LaHood called it an "honor and a privilege" to serve and said he'd stay until a successor is confirmed. He cited what he said were the department's achievements, including a Distracted Driving Initiative and a rule to combat pilot fatigue.

"I've told President Obama, and I've told many of you, that this is the best job I've ever had," LaHood said.

Obama said in a statement that he and LaHood were "drawn together by a shared belief that those of us in public service owe an allegiance not to party or faction, but to the people we were elected to represent."

And he added, "every American who travels by air, rail or highway can thank Ray for his commitment to making our entire transportation system safer and stronger."

Among the talked-about candidates to replace LaHood are Los Angeles Mayor Antonio Villaraigosa.