NEW YORK (AP) — Democratic Sen. Evan Bayh of Indiana will endorse Hillary Rodham Clinton's presidential bid on Monday, sources close to both lawmakers say.

A colleague of Clinton's on the Senate Armed Services Committee, Bayh actively pursued a possible presidential bid until late last year, when he dropped out of the race amid evidence that Clinton and Sen. Barack Obama of Illinois were building formidable campaign organizations.

"The odds were always going to be very long for a relatively unknown candidate like myself, a little bit like David and Goliath," Bayh said at the time.

Clinton and Bayh traveled together to Iraq in January, just before Clinton announced she would seek the Democratic nomination. Bayh is one of several potential presidential contenders who abandoned their own bids to endorse her.

Former Iowa Gov. Tom Vilsack dropped his bid last winter to become the New York senator's campaign chairman. Last week, retired Gen. Wesley Clark also announced he was backing Clinton.

Bayh, a former governor of a Republican-leaning state, is in his second term in the Senate. A centrist who won re-election with 62 percent of the vote in 2004, he is likely to be considered for the Democratic ticket in 2008.