Baucus said the he and former state office director Melodee Hanes began dating when they were both separated from their spouses. The Montana Democrat said they did not have an affair.

In a statement issued by his office Saturday, Baucus said he recommended Hanes to become Montana's U.S. attorney because she is a highly qualified prosecutor who tried more than 100 jury trials, and said she is widely regarded as an expert in child abuse prosecution.

Baucus, who is helping Democrats expand health care, nominated Hanes for the post in March. But she later withdrew, saying she had been presented with other opportunities she couldn't pass up. Baucus said the two now live together in Washington.

EARLIER: Senate Finance Committee Chairman Max Baucus was romantically involved with a former staffer when he recommended her earlier this year to become the next U.S. attorney for Montana, a spokesman said.

The Montana Democrat and his former state office director Melodee Hanes began their relationship in the summer of 2008 after Baucus separated from his wife, Ty Matsdorf told The Associated Press late Friday.

Baucus, a Senate leader helping to shepherd President Barack Obama's efforts to expand health care, nominated Hanes for the U.S. attorney post in March. But she later withdrew, saying she had been presented with other opportunities she couldn't pass up.

Baucus had submitted six names to a third-party reviewer, who whittled those to Hanes and two others. Matsdorf said the senator sent the three names to the White House with no ranking to select a nominee.

Matsdorf said Baucus' relationship with his girlfriend had nothing to do with his decision.

"Senator Baucus recommended each of the three candidates based solely on qualifications, and merit, knowing whichever one the White House selected would serve Montana well," Matsdorf said.

The spokesman said Baucus and Hanes decided during the nomination process that she should withdraw her name because the couple wanted to live together in Washington, which they later did.

The senator disclosed the circumstances surrounding the nomination after inquiries from Mainjustice.com, a news Web site focusing on the Justice Department that first reported Baucus' relationship with his nominee.

Baucus has played a major role in managing the Democrats' health care overhaul efforts. He joined Senate debate Saturday on the health bill, receiving a nod of support from Senate Majority Leader Harry Reid.

"Max is a good friend, an outstanding senator and he has my full support," Reid said in a statement released by his spokesman.

Republican Sen. Lisa Murkowski of Alaska said she didn't think the issue would affect Baucus' leadership in the health care debate. "I don't think it's going to distract from the substance of the debate," she said in a brief interview Saturday during the Senate's rare weekend session.

Baucus and his ex-wife Wanda announced last April that they planned to divorce after 25 years of marriage, his second. In a joint statement, they said they had "parted ways amicably and with mutual respect."

Hanes started working for Baucus in 2002 and was his state director before leaving his office earlier this year for a Justice Department position.

"Mel is supremely qualified and she got to her current position based solely on her merit," Matsdorf said.

President Barack Obama eventually nominated Helena attorney Michael Cotter for the U.S. attorney post, which supervises prosecutors of all federal crimes committed in Montana and the state's seven Indian reservations. Cotter is awaiting confirmation.

Word of Hanes' nomination follows other recent disclosures of romantic liaisons by political leaders, including South Carolina Gov. Mark Sanford, Sen. John Ensign, R-Nev., and two-time Democratic presidential hopeful John Edwards.

Sanford faces a possible impeachment following his affair with a woman in Argentina. Ensign, who has acknowledged in June to having an affair with a former member of his campaign staff, has made it clear he intends to serve out his second term. Edwards' political career was damaged when he acknowledged last year he had an affair with a videographer in 2006. The admission came just months after Edwards dropped his second presidential bid.

Baucus was elected to the Montana House in 1973 and to the U.S. House in 1974 and 1976. He was elected to the U.S. Senate in 1978 at age 36, and his current term runs until 2014.

The senator has played increasingly visible roles in Congress, sometimes willing to buck his Democratic Party on certain issues. He seems to take the position that the state that sent him to the Senate for five terms is fundamentally conservative and its voters want someone willing to vote outside the party line.

Most recently Baucus has been at the center of an effort to move sweeping health care legislation through the Senate with a bill aimed at meeting Obama's goal of overhauling the nation's health care system to cover 30 million more Americans over the next decade.

On Friday, Baucus went against his party and backed a Republican effort to eliminate a long-term care insurance program to help seniors and the disabled. Republicans argued that the new plan would be a drain on the federal budget.