Although there is already a field of GOP candidates lining up to take on Nelson, Republican leaders, including Senate Minority Leader Mitch McConnell (R-Ky.), are reportedly seeking to recruit Gov. Dave Heineman (R) to join the race, ostensibly to scare Nelson out of running.
Spending by Crossroads against Democratic candidates competing in 2012 races has become so prodigious that in many cases, it has dwarfed early spending by party committees and candidates' own campaigns. The group has pledged to spend $20 million on ads undercutting Obama.
Crossroads announced last week it was hitting Democratic Senate candidates in Missouri, Massachusetts, Montana and Nebraska with more than $1 million in ads. One month earlier, it spent $2 million in those states and $2.6 million in another five swing states to attack Democrats.
Watch the ad targeting Obama: