From NBC's Mark Murray and Ken Strickland
New Mexico Sen. Jeff Bingaman (D) will not run for re-election in 2012, according to two sources with knowledge of his decision.
Bingaman was first elected in 1982, and he's currently serving his fifth term in the U.S. Senate.
Democrats say they're confident they will keep the Senate seat, especially in a presidential year (Obama won New Mexico with 57% of the vote in 2008). A top Dem candidate to replace Bingaman would be two-term Congressman Martin Heinrich (D).
Bingaman joins a 2012 Senate retiree list that includes Kay Bailey Hutchison (R-TX), Kent Conrad (D-ND), Joe Lieberman (I-CT), Jim Webb (D-VA), and Jon Kyl (R-AZ).