One instance in particular has stuck in the craw of many of his colleagues. This summer, DeMint forced a late vote on an HIV/AIDS bill, but then decided to leave the chamber, forcing his colleagues to carry on the fight without him.
Then, in July, DeMint forced a rare Saturday vote on a massive housing bill. Although he did show up for that vote, many Senate Republicans had had enough with his tactics at that point, they said.
I think he really jumped the shark with the Saturday vote, one GOP leadership aide said, adding that while coming in for a weekend vote is not necessarily a big deal for these guys, DeMint ruffled a lot of feathers by forcing the AIDS vote and not showing up.
Roberts also said DeMints use of the Republican Steering Committee to take on other GOP Senators has also caused tensions within the Conference.
Since taking over the RSC in the 110th Congress, DeMint has used the committee as a base for launching a series of conservative crusades, to varying degrees of success. DeMints first major feat came during the 2007 immigration battle when he, along with a handful of vocal conservative Senators, such as Sen. Jeff Sessions (R-Ala.), successfully rallied the partys base to defeat a massive immigration reform proposal backed by the White House and eventual presidential nominee Sen. John McCain (R-Ariz.).
The Steering Committee worked as a base of operations for DeMint and his allies to not only attack the bill, but also coordinate with outside groups to bring pressure on Republicans they believed were not toeing the conservative line.
DeMint really used the immigration fight as a template for future skirmishes on issues such as earmark reform, a GOP leadership aide said.
But DeMint also increasingly has used his position as the RSC chairman to take his conservative fight to other Republicans most recently, his effort to expel Stevens for his seven-count federal felony conviction in October. Stevens has long been a target of DeMints efforts to reform the party, given Stevens extensive use of the earmarking system to pump billions of federal dollars into his home state.
But DeMints decision to operate an independent group funded by Republicans that would basically be in opposition to other Republicans rubbed other members of the Conference wrong, Roberts said, arguing that now is not the time for ideological purges. When youre an endangered species, you dont purge like the Kremlin, Roberts said.
Other Republicans point to DeMints increasingly defiant stance against his partys leadership, particularly in the wake of the elections, as the primary reason for his freshly soured relationship with the Conference.
For instance, following DeMints criticism of McCain for abandoning conservative principles, Sen. Richard Shelby (R-Ala.) ripped into his colleague, telling CNN that, I think my friend Sen. Jim DeMint should keep this stuff in the caucus and not be out beating up on fellow Republicans.
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.