GOP senators and aides were quick to note even before Tuesday's result that DeMint's spending appeared to have done little for Stenberg.
"This one will leave a mark for anyone who has been peddling the conservative kingmaker bit," one senior GOP campaign operative said.
Meanwhile, the NRSC and Cornyn argue that Fischer may be their best candidate against former Democratic Sen. Bob Kerrey, D-Neb.,
A similar divide will play out in the May 29 Texas Senate GOP primary, where DeMint's PAC and the Club for Growth are among conservatives backing former state Solicitor General Ted Cruz, against Lt. Gov. David Dewhurst, who is considered the frontrunner. Republicans argue either GOP candidate can cruise to the nomination.