Nelson got a bit of a break on Thursday, when Gov. Dave Heineman announced that he would not run. Previous polling had shown Nelson being very vulnerable in a test match against Heineman in this red state.
But Bruning was quite ready to jump in, and others might be on the way.
Nelson's home state of Nebraska has not voted Democratic for president since the Lyndon Johnson landslide of 1964. In 2008, John McCain carried it by 57%-42%.
A Rasmussen poll from December 2009, in the heat of the health care debate, showed Nelson losing two-to-one against Heineman. In addition, an Omaha World-Herald poll from January 2009 gave Nelson an approval rating of 42% and disapproval of 48%, with a majority opposed to his vote for health care reform.
(Via Roll Call.)