The decision by Sen. Ben Nelson (D) of Nebraska not to run for reelection in 2012 is a 'blow' to Democrats' efforts to retain their Senate majority, analysts say.
Consumer advocate Elizabeth Warren filed paperwork Thursday to form an exploratory committee for a US Senate run in Massachusetts. Republican Scott Brown currently holds that seat.
Wisconsin Sen. Herb Kohl says he's retiring after his fourth term ends in 2012. He is the sixth Democrat-aligned senator to do so, compared with only two Republicans.
Former governor and current DNC Chairman Tim Kaine declares his candidacy for the Virginia Senate race, joining former governor and senator George Allen (R).