Sen. Tom Harkin, a Democrat who has represented Iowa in the U.S. Senate since 1984, will not seek re-election in 2014.
He told the Des Moines Register on Saturday, "To walk away from this position and this power is not an easy thing. But I think it's the right thing. And I have two years left. I'm not passing the torch sitting down, it's a running relay. I intend to be very active over the next two years."
Before serving five terms in the Senate, Harkin represented the state in the U.S. House and served in the Navy. The 73-year old would be 81 years old at the end of a sixth term.
He told the Register he has "mixed feelings" about this decision, but said, "You know what, it's somebody else's turn."
Democratic Senatorial Campaign Committee Chairman Michael Bennet issued a statement saying he has "seen firsthand Tom Harkin's strong commitment to the people of Iowa" and appreciated "that Senator Harkin has made this decision so early in the cycle, giving us ample time to recruit a strong Democratic candidate for this seat."
At this point, Democrats will be defending 21 of the 35 Senate seats up for election in 2014. They currently have an advantage with 55 seats in the Senate (including two independents who caucus with them) to Republicans' 45 seats.
Harkin's announcement comes after Sens. John D. Rockefeller IV, D-West Virginia, and Saxby Chambliss, R-Georgia, each announced this month they will not seek re-election in 2014.
Harkin won his 2008 election with 63% of the vote.
Iowa's other senator is Republican Chuck Grassley, whose sixth term expires in 2016. Grassley is 79 years old.
In his second bid for the U.S. House - 1974, his first successful run - Harkin worked a variety of jobs as part of his campaign to communicate he understood people's concerns.