The new dynamic has been perhaps most apparent within the Republican National Committee, where divisions over party leadership have simmered even at a time when the party is poised for big gains.
"Many congressional Republicans and governors no longer trust [RNC chairman Michael] Steele as their spokesman," wrote Fred Barnes, executive editor of The Weekly Standard, in a Wall Street Journal column. "They tend to work around the RNC rather than engage Mr. Steele."
"What the RNC isn't doing, well-financed outside groups like Americans for Prosperity and the Republican Governor's Association are," he said.
But how long this fractured relationship will continue is unclear.
"On the Republican side what we are seeing is an abnormality, a chasm between the RNC chairman and the rest of the establishment," said Meredith McGehee of the Campaign Legal Center, suggesting that the dynamic could return to the status quo in 2012.
In the meantime, national party leaders caution that they should not be counted out.
"The parties have become, I think, much more relevant in some subtle ways having to do with information processing and micro-targeting," said Ansolabehere.
The parties' extensive voter e-mail databases and networks with state party groups, which can help mobilize supporters and hone messaging, are advantages not held by outside groups, he said.
"The parties can come in with information that the candidates just didn't have and say we can run this and do it very well."
The parties also continue to demonstrate robust fundraising and play an important role in political messaging in the campaign. The Democratic National Committee has sent about $6.6 million to each of its House and Senate campaign committees, according to the Hotline's Jeremy Jacobs, while the RNC has transferred $2 million to its House and Senate campaign arms.
The DNC had $13.4 million on hand heading into the final month of the campaign, and the RNC had $4.6 million, according to Federal Election Commission reports.
Brendan Glavin of the Campaign Finance Institute cautioned that the sizable disparity in spending between non-party and party groups this year could be misleading.
"It's not as if it's all new money in the campaign," said Glavin. "In the past, some of this money was already in the system, but it wasn't reported." He noted that disclosure requirements make it difficult to track the change.
Bottom line? The parties still have "plenty of bullets left in their clip," said Levinthal.