(CNN) - Democratic Rep. Jerry Costello will not run for reelection to Congress in 2012, he announced Tuesday.
The twelve-term Illinois congressman, who serves as dean of the Illinois delegation, said he is leaving the House to pursue "other interests and opportunities that may come along."
"It has been a privilege and an honor to serve in the U.S. Congress for the past 23 years," Costello said in a statement. "However, I said when I was elected in 1988 and many times since that I did not intend to stay in Congress forever as I had other interests that I wanted to pursue."
Costello is the fifth House member, all of whom are Democrats, to announce his retirement this cycle, according to Roll Call. Another 14 members are running for another office.
The typically blue district in the Southern part of the state supported President Barack Obama with 56% of the vote in 2008 and then-Democratic presidential candidate John Kerry with 52% of the vote in 2004.
But Andrea Bozek, spokeswoman for the National Republican Congressional Committee, said Costello's retirement was a reaction to his vulnerability.
"Jerry Costello saw the writing on the wall and knew that he couldn't defend his decades of job-destroying policies that have made our economy worse," Bozek said in a statement. "After years of listening to Jerry Costello pay lip service to fiscal responsibility, Illinois working families will finally have the chance to elect a candidate that truly represents their values."
Democratic Rep. Steve Israel, who serves as chairman of the Democratic Congressional Campaign Committee, thanked Costello for his service and predicted Democrats would maintain control of the district.
"This is a strong Democratic district that both President Obama and Senator Kerry won and we look forward to electing a Democrat next November who will represent middle class families and fight to create local jobs and grow the economy," Israel said in a statement.