Conservative Sen. Jim DeMint’s (S.C.) high-profile campaign to influence GOP primaries this cycle has had a minimal impact on National Republican Senatorial Committee Chairman John Cornyn’s (Texas) job to win races on a politically diverse, national playing field and rebuild a 41-member Conference.

But for an institution that largely functions on trust and seniority, DeMint’s challenge to Cornyn — particularly in key Republican primaries that could determine the party’s fortunes this November — has irked many of the South Carolinian’s colleagues, the NRSC chairman included. DeMint’s political action committee even grades the votes of his fellow Republicans in an online scorecard.

In interviews, Cornyn and DeMint brushed aside the suggestion that there’s any rift between them or that they don’t get along. One Senate Republican, echoing what’s almost a refrain among GOP Senators, dismissed the significance of DeMint’s efforts to elect conservative, anti-establishment candidates, saying “that’s just Jim being Jim” while arguing that the one-term Senator isn’t likely to get in the way of the NRSC’s efforts to elect GOP Senators this fall.

DeMint, a former House Member elected to the Senate in 2004, said he’s simply trying to engender party unity and keep conservative voters in the fold. Cornyn responded that the primary elections will serve to validate or invalidate DeMint. “Before the primary, it’s fine for people to support different candidates,” Cornyn said last week. “But after the primary is over, we’re all going to have to support the Republican candidate — and that’s where the rubber will meet the road.”

Often the source of intraparty consternation, DeMint acknowledged that his actions have caused some friction.

But he said he speaks to Cornyn regularly and that the two usually agree when it comes to Senate primary contests. DeMint argued he has no interest in imposing a “litmus test” or a “purity test” for GOP candidates. In fact, DeMint said plainly that he’s prepared to back the winners of this year’s GOP primaries.

“The way to a big tent, which is what I want — a majority — is to get Republicans who really believe in what we say we believe and do what we say, because that’s attractive to people all over the country,” DeMint said. “We’ve got a lot of great new faces in the party across the country that might not get a shot unless a few of us go out and try to help them at least get up there on the stage and compete. If they lose, we’ll all be together in the general.”

DeMint, through his Senate Conservatives Fund PAC — for which he raised $1.3 million in 2009 — has funneled nearly $300,000 to Republican candidates this cycle. Judged per candidate, DeMint’s contributions are relatively insignificant and haven’t transformed any also-ran into a player, a fact his critics are quick to point out.

But the South Carolinian’s support has lent some candidates much-needed credibility and national attention. DeMint’s campaigning also has helped focus media attention on the ideological struggle within the GOP these days, a potentially problematic divide for a party that is eyeing significant gains on Nov. 2.

Prime examples include the Florida Senate GOP primary, where DeMint is backing former state Speaker Marco Rubio, a newfound darling of conservatives, over moderate Gov. Charlie Crist, and in California, where he endorsed obscure state Assemblyman Chuck DeVore over wealthy former Hewlett Packard CEO Carly Fiorina. In Florida, Cornyn moved early last year to support Crist when he was still popular and the GOP brand was in shambles, and in the Golden State, Cornyn is backing Fiorina.

Cornyn’s early endorsement of Crist angered some conservatives. But DeMint subtly defends the NRSC chairman, saying Cornyn made the only logical decision at a time when viable Republican candidates were hard to recruit. DeMint added that Cornyn’s decision had the important effect of scaring top-tier Democrats out of the race in what is a crucial open seat.

DeMint did not offer similar praise for Cornyn’s backing of Fiorina, seen by experienced California political observers as the only candidate with the financial resources and personal profile capable of beating Sen. Barbara Boxer (D) in such a solid blue state with several expensive media markets. But DeMint said his endorsement was made with the health of the GOP in mind, arguing that only through a dynamic primary can the party break through in left-leaning states such as California and New York.

As for declining to endorse incumbent Sen. John McCain (R-Ariz.) in his intraparty fight against conservative former Rep. J.D. Hayworth, DeMint was vague. Re-electing incumbents, of course, is Cornyn’s No. 1 responsibility. DeMint, who is running for a second term this year, falls into that category.

“That’s not what I’m doing this cycle. I’m not endorsing all Senate candidates,” DeMint said. “I’m trying to pick a few people in some areas, insurgents — a lot of times underdogs — to try to help.”

Cornyn declined to criticize DeMint over the move, saying only: “My first responsibility as chairman is to help our incumbents. I guess he sees his message as different.”

Senate Republican Policy Committee Chairman John Thune (S.D.), a conservative who considered heading up the NRSC in the 2008 cycle, said the GOP is strong enough to handle contested races — and that they ensure the party’s eventual nominee is battle-tested. But Thune, who is also up for re-election this year, said he hopes DeMint spends as much time fighting the Democrats this fall as he did waging war against fellow Republicans in the primaries.

“I think that we’re an entrepreneurial party with a lot of different points of view. DeMint’s out there in a number of these races — he’s active. And, I think that’s his prerogative,” Thune said. “That’s obviously not going to be the direction in which, in some cases, the NRSC may be going. … I don’t have a particular problem with that. I just hope that in the end we’re working on electing more Republicans to Congress.”

While DeMint has become something of a folk hero among grass-roots conservatives, he is something of a one-man band in the Senate. Most of DeMint’s Republican colleagues are similarly conservative, but his tactics — he regularly wages one-man floor fights — often rub his leadership and his colleagues the wrong way.

DeMint’s Senate critics often point to the time he used Senate rules to force a weekend vote and then didn’t even bother to show up.

Still, DeMint isn’t always out of the mainstream. He endorsed Sen. Scott Brown (R-Mass.) —a fiscal conservative but social moderate who already sided with Democrats on the $15 billion jobs bill —and contributed to his special election campaign.

A Republican operative with experience working on Senate races said DeMint is far less dangerous to the GOP’s 2010 electoral prospects than some might think.

“It’s not that helpful, but it’s probably not too much of a distraction. He did the same thing last cycle, but our party couldn’t recruit anybody so it really didn’t matter,” the second Republican operative said. “His impact is nothing like that of a [former Alaska Gov. Sarah] Palin, for example, because he is still unknown.”