Castle said Cochran “needs to be careful since these tea party groups can bring in a lot of money in a rush. . . . Even if you’re more prepared than I was, and the surprise is sort of gone, you’ve got to pay close attention to what they’re doing.”

Cochran’s advisers and advocates insist the money is all for naught. Although they acknowledge the race is tightening, they also argue that Mississippians will not turn out a senator who, as a member and former chairman of the Appropriations Committee, has delivered time and again for his poor and rural state, such as after Hurricane Katrina ravaged the Gulf Coast.

“He can just accomplish so much more than Chris McDaniel, and I think people see a contrast in that we know we can count on Senator Cochran,” said Henry Barbour, a nephew of former Mississippi governor Haley Barbour (R) who is running Mississippi Conservatives, a pro-Cochran super PAC.

He recalled an exchange, reported in February by Politico, in which McDaniel told an audience at the University of Mississippi: “I’m not going to do anything for you. I’m going to get the government off your back, and then I’m gonna let you do it for yourself.”