INDIANAPOLIS -- With his family at his side, Democratic Sen. Evan Bayh announced Monday afternoon that he will not seek re-election to a third term in the seat he has held for more than 10 years.

Bayh, 54, announced the decision Monday at a news conference at Indiana University Purdue University-Indianapolis, citing increased rancor in Congress and his distaste for its "narrow ideology" and "strident partisanship."

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"After all these years, my passion for service to my fellow citizens is undiminished, but my desire to do so by serving in Congress has waned," Bayh said. "To put it in words most Hoosiers can understand: I love working for the people of Indiana, I love helping our citizens make the most of their lives, but I do not love Congress. I will not, therefore, be a candidate for election to the Senate this November."

Indiana Democratic leaders said they were blindsided by the decision.

"I was shocked and saddened … for the people of Indiana and our country, but I'm focused now on moving forward," said Dan Parker, Indiana Democratic Party chairman

Bayh had amassed $13 million for the re-election campaign and was polling favorably, officials said.

"Until 10 minutes ago, I was absolutely certain Evan Bayh would be the future U.S. senator, and the continued U.S. senator," said Indiana House Speaker Pat Bauer. "His polls are excellent. His rapport with the people is excellent."

Bayh has held the senate seat since 1998. He previously served as Indiana's governor and secretary of state. He considered running for president in 2008, but dropped out and endorsed Hillary Clinton.

Bayh was later among several people who then-candidate President Barack Obama considered for a running mate.

Bayh had been under scrutiny in recent weeks, and Republicans felt that they stood a good chance of picking up his Senate seat in a conservative state in an environment in which there appears to be a groundswell nationally of dissatisfaction with Obama and Democrats in Congress.

Bayh has supported much of Obama's agenda, including health care legislation and the economic stimulus plan. Obama praised Bayh's role in the Senate.

“For more than two decades, Evan Bayh has devoted his career and his life to serving his fellow Hoosiers. During that time, he has fought tirelessly for Indiana’s working families, reaching across the aisle on issues ranging from job creation and economic growth to fiscal responsibility and national security," Obama said in a statement released Monday afternoon. "I look forward to continuing to work with him on these critical challenges throughout the rest of the year.”

Former Sen. Dan Coats is among several Republicans seeking to win that party's nomination. Coats decided not to seek re-election in 1998, avoiding a race with then-Gov. Bayh.

State Sen. Marlin Stutzman, Fishers businessman Richard Behney, John Hostettler and Don Bates Jr. are also seeking the Republican nomination for senator.