Sen. Jim DeMint doesn’t think people much care about his presidential endorsement (“I don’t like the suggestion that there’s lots of people out there waiting for me to tell them how to vote,” he says). But the fact is people do care — a lot. A nod from DeMint is one of the most coveted endorsements of the 2012 presidential cycle. Not only is DeMint the most popular Republican in the critical primary state of South Carolina, he has become a national hero among conservatives thanks to his bold support of conservative insurgents running for Senate in 2010. Newly elected Sens. Marco Rubio, Pat Toomey, Rand Paul, Mike Lee and Ron Johnson can all trace their improbable victories to early support from DeMint and his Senate Conservatives Fund.

It is this success that has led DeMint, after much contemplation, to decide that he will not endorse anyone in the 2012 GOP presidential primaries. “I want to announce that I am very unlikely to endorse a candidate in the presidential race,” DeMint told me in an interview this weekend. The most disappointed GOP contender may be Mitt Romney, who received De­Mint’s endorsement in 2008 and could have used the senator’s support to woo skeptical conservatives this time around. Why did DeMint decide not to endorse Romney again? “It’s a different race, different people in it, different time for our country,” he said, adding, “I would be very comfortable supporting any of . . . [our candidates] for president.”

Note that DeMint leaves himself a little wiggle room. When asked why, he said, “As we get into next year, if we have two at the top and one is clearly the conservative and one’s not . . . I might look at it again. But my commitment right now is to stay out of it.”

The reason he is staying out, DeMint said, is that “I’ve got to keep my focus on electing conservatives to the Senate who are going to come in here and help us change the spending culture and help our new president turn the country around.” The tipping point for DeMint came last week, when he watched 32 of his Republican colleagues vote with Democrats to kill an amendment offered by Sen. Tom Coburn (R-Okla.) to cut $1 billion from the Rural Development Agency, while 11 Republicans voted with Democrats against eliminating a paltry $6 million in funding for the Small Community Air Service Development Program. “I’ve realized over the last week, as I’ve seen how some of the votes were cast in the Senate, [that] we had some Republicans who were going to resist any cuts in programs.”

The lesson, DeMint said, is that while conservatives have made progress in the Senate, “We’re not there yet. We just need some more numbers.” He said he believes his role in 2012 is to unite conservatives behind the right candidates in critical Senate races. Notwithstanding last week’s votes, De­Mint said, he is optimistic and believes conservatives are on the verge of reaching “critical mass” in the Senate. The arrival of newly elected conservatives has “brought out the best in 20 others” in the GOP conference. If he can help elect five or eight more like them in 2012, DeMint said, it “would give us a conservative consensus — a critical mass of conservatives . . . who understand the mandate and the necessity of actually devolving the role of the federal government.”

Another reason for his decision, DeMint said, is that staying out of the presidential primaries will give him greater freedom to hold the next president’s feet to the fire, if a Republican wins in 2012. “I’m not going to be beholden to anyone,” DeMint said. He will lay out conservative principles during the campaign, and “if a candidate wins and is not doing those things, then I think I have a good platform to challenge that president to be true to what America elected us to do.”

DeMint said he believes that getting conservatives elected to the Senate could mean the difference between success and failure for whoever succeeds President Obama. “I want to do better for our next president than we did for George Bush,” he said. Bush “had a Congress that wanted to spend money, and if he wanted anything done, he had to agree to that spending . . . . I want our next president to have a strong conservative Senate that can push them in the right direction rather than the wrong direction. ”

So far, DeMint has endorsed two candidates — Josh Mandel in Ohio and Ted Cruz in Texas — and his Senate Conservatives Fund has raised over half a million dollars for each. “Beginning next week I’m going to start to endorse other candidates,” DeMint told me. With support from grass-roots conservatives, he said, “collectively, I think we can raise over $10 million and focus that on five to eight races. And by doing that I know we can change the Senate . . . . Five or eight more like . . . [Marco Rubio, Pat Toomey and Rand Paul] and a Republican president, we can turn our country around . . . . It is really now or never for our country. We’re not going to get another bite at this apple. ”