"Republicans tried to sell a bill of goods that Nebraska is gone, and that's not true," one Democratic strategist said. The strategist said the DSCC's support for Nelson has nothing to do with trying to persuade him to run for re-election: "He knows there's going to be resources for him."
Johnson said Nelson has not asked for any assistance from Washington, D.C., Democrats, although he is "glad" for the help.
Nelson, a centrist Democrat and former governor, was for several years a popular figure in his Republican-leaning state. But the Senator has been under fire ever since he played a crucial role in the passage of President Barack Obama's health care law.
Republican strategists view Nelson's seat as one of their top pickup opportunities — regardless of whether the Senator stands for re-election. And they dismiss recent optimism emanating from the DSCC as misplaced.
Of course, Nelson is not the only vulnerable Democrat going into 2012.
The DSCC is defending 23 Democratic-held seats this cycle, including many in states that either lean Republican or tend to swing with the political tide — a factor that, at this point, appears to be in the GOP's favor.
With multiple seats conceivably threatened, Murray could be forced to make tough decisions about where to invest, although the DSCC has continued to outraise the National Republican Senatorial Committee and took in about $4 million more in the third quarter.
Sen. Jon Tester (Mont.), one of the potentially vulnerable Democrats likely to take heavy political fire from Republicans next year, has also seen ads run against him at home, including by Crossroads GPS during the summer debt ceiling debate.
Despite having already committed to running for re-election, it is unclear whether they have received equal attention from the DSCC. Tester, at least, seemed unconcerned.
"That really is [the DSCC's] call," he said. "It doesn't really matter."
Republicans contend that the DSCC's decision to get involved in the Nebraska race in the fall of the off-year proves the committee is worried.
"When you look at the massive spending by national Democrats in Nebraska, it certainly makes you wonder why they apparently don't place the same premium on Claire McCaskill and Jon Tester's re-election campaigns as they do for Ben Nelson," NRSC spokesman Brian Walsh said.
When asked how she decides who to help "early," Murray said that she's "defending 23 seats and I'm working hard to make sure we defend them all."
Sen. Bob Menendez, who served as DSCC chairman last cycle and is running for re-election this year, said Murray may have no choice but to invest early to protect certain incumbents, given the activity of third-party GOP groups.
"There are moments where you have to spend early to make sure a race doesn't get away from you," the New Jersey Democrat said. "Probably with the third-party expenditures taking place in his race, the DSCC probably felt that at this time they had to get engaged to make sure that race doesn't get away from them."
Former Sen. Scott Brown, R-Mass., candidate for U.S. Senate in New Hampshire, holds his hand over his heart during the singing of the national anthem as he waits to take the stage for his town hall campaign rally with Sen. John McCain at the Pinkerton Academy in Derry, N.H., on Monday, Aug. 18, 2014.