All the pieces are in place for a re-election bid, but Nebraska Sen. Ben Nelson is wavering on whether he'll seek a third term in 2012 or retire _ a decision that could have a big effect on Democrats' chances of holding their Senate majority.

Nelson told The Associated Press on Thursday that he'll make a decision over the holiday season. In the meantime, he's piled up campaign cash, hired a campaign manager and watched his party spend more than $1 million on ads supporting him.

But Nelson, a conservative Democrat, has told friends and supporters he's not a lock for another run and has expressed frustration with the inability of a divided Congress to pass meaningful legislation.

"He's alluded to a lot of frustration back in Washington," said former Omaha Mayor Mike Fahey, a Nelson supporter. "There's a lot of frustration with him and independent-minded senators about the ability to get things done."

Fahey said he expected Nelson's happiness on the job, as well as family concerns, to factor heavily in his decision.

Nelson's decision will have important consequences for Democratic hopes of maintaining control of the Senate. Republicans need to net four seats in 2012 to take back the upper chamber.

Republicans see his seat as a pickup opportunity either way: They believe the state has tilted further to the right in recent years and think Nelson's vote for President Barack Obama's signature health care legislation will weigh him down.

But Nelson, a two-term governor before winning a Senate seat, would give Democrats a fighting chance. Nelson dipped in polls after the health care debate, but he has shown an ability to rebound after being down in statewide races before.

Guy Cecil, the executive director of the Democratic Senatorial Campaign Committee, said Thursday his organization is still planning for Nelson to run but will await his announcement.

For his part, Nelson said he'll act as if he's running until he decides he's not.

"The campaign is moving as planned," Nelson said. "We are raising money, hiring staff."

Nelson's preparation has left him with a healthy cash advantage should he decide to go for a third term. He has more than $3 million cash on hand, about twice his nearest competitor, and has the luxury of stockpiling money while Republicans have a crowded primary that includes Don Stenberg, the state's treasurer, Jon Bruning, the attorney general, and Deb Fischer, a state senator.

Nelson said he is not making his intentions clear, in part, because "campaigns are too long," he said.

"I don't want everything I say or do viewed through the prism of re-election," he said. "Perhaps this is the norm for my colleagues, but it is not the way I have operated in the past."

Fahey said Nelson's kept close counsel on his decision. But he said he believes Nelson is leaning more toward running than not and said Nelson is behaving the same way he has when he's run in past elections.

"I think he's absolutely prepared himself to run," Fahey said.