WASHINGTON — Two friends of labor — Democratic Senators Kent Conrad (N.D.) and Joseph Lieberman (Conn.) — say they will retire at the end of the 112th Congress in 2012. Conrad is completing his fifth six-year term; Lieberman completing his fourth six-year term.

These announcements follow the retirement announcement of Republican Sen. Kay Bailey Hutchison of Texas, the senior Republican on the Senate Commerce Committee, who said she will retire in 2012 when her third six-year term ends. The Senate Commerce Committee has oversight of many rail, transit, air and bus issues. She is considered a moderate Republican.