Their feud has been one of the most enduring — and important — clashes within the ranks of the Republican party. Team McConnell thinks DeMint is a self-destructive showboat whose tactics, such as the government shutdown, can lead only to disaster. Team DeMint thinks McConnell is a petty, vindictive tyrant who pushes a mushy agenda behind the scenes. The battle raging in Kentucky is the culmination of seven years of on-and-off conflict.

It would be a mistake to think the feud is merely a personal grudge match or an escalating series of retaliatory strikes. Over the years, DeMint has often seemed almost oblivious to how his aggressive tactics would be received by GOP colleagues, focused only on the merits of his arguments. McConnell, meanwhile, is a calculating man who exercises power efficiently and is unlikely to be swayed by wrath.

Although DeMint and McConnell have had their share of tense personal interactions, a good deal of the fighting has occurred at the staff level. In particular, McConnell aides put much of the blame for DeMint’s alleged transgressions on Hoskins, a former DeMint chief of staff who now operates SCF from California’s Central Valley independently from DeMint. “Matt Hoskins can’t go more than three paces in this town without letting people know how he feels about Mitch McConnell,” says a senior McConnell operative. DeMint, then the group’s chairman, vowed in 2010 not to use the political action committee to target Republican incumbents, and sources familiar with the matter say he had no input on Hoskin’s decision to back Bevin.