Oklahoma's U.S. Rep. Dan Boren won't seek re-election in 2012

He spent $1.8 million in the last election cycle to win re-election against unknown Republican Charles Thompson, who spent less than $50,000.

Boren is a leader of the Blue Dog Coalition, a group of moderate and conservative Democrats whose ranks were cut nearly in half in the 2010 elections, when Republicans regained control of the House. Boren said shortly after the elections that he wouldn't support Pelosi as minority leader, and he voted against her.

Boren never officially endorsed Obama, who lost every county in Oklahoma in 2008, and he strongly opposed some of the president's biggest priorities, including health care reform and cap-and-trade legislation. He did support the stimulus bill.

But even a district thought to be safe for Democrats — it includes most of what used to be known as Little Dixie, the Democratic stronghold in the state — has proved to be challenging as Oklahoma grows more conservative.

Obama praised Boren's service on Tuesday, saying he had “exemplified a commitment to creating jobs and economic opportunity for his constituents and rural communities, all the while continuing his family's long line of public service and dedication to the state of Oklahoma.”

The affable and mild-mannered Boren is the son of University of Oklahoma President David Boren, who is a former U.S. senator and Oklahoma governor; Boren's grandfather, the late Lyle Boren, served in the U.S. House from 1937-47.

In Congress, Boren has focused on national security, tribal and energy issues. An avid sportsman and a member of the National Rifle Association board, Boren has also been a strong proponent of gun rights.

The National Republican Congressional Committee announced that it would target Boren's seat in the last election, but never followed through with any major effort to defeat him. Republicans are expected to make a strong push to win the seat next year.

Paul Lindsay, a spokesman for the GOP congressional committee, said Tuesday, “Dan Boren is the last of a dying breed of Democrats who are no longer welcome in a party driven by the job-destroying agenda of President Obama and Nancy Pelosi.”