DeMint shook up the Senate but leaves a disenchanted GOP leadership Still, DeMint's strategy came with serious limitations. And Thursday, some of his closest associates said these may have spurred DeMint's decision to leave Congress during his second term as a senator. The Senate's ultimate outsider, they said, may have decided he needed to go farther outside. "Jim is the guy who's passionate, [with] conviction, [an] idea guy who has a vision for the country and believes it's one worth fighting for," said former senator and presidential candidate Rick Santorum (R-Pa.), who was an ally of DeMint's in the Senate. "I think that was his motive to go to the Senate" in the first place, Santorum said. What this shows is that maybe he's looking at the Senate as not the best place to do that right now. DeMint, 61, is a native of Greenville, S.C., who worked in business before he was elected to the U.S. House in 1998. Five years later, he won the Senate seat vacated by retiring Democrat Ernest F. Hollings, a change that reflected South Carolina's broader political shift from bastion of the Democratic "Solid South" to epicenter of a deep-red modern conservatism. In the Senate, DeMint has been distinguished by his strident attacks on Democrats: The health-care debate, he predicted, would be President Obama's "Waterloo." DeMint said Obama was the "world's best salesman of socialism." But many of DeMint's most important confrontations have been with Republicans. Under President George W. Bush, he helped derail an immigration proposal supported by Bush and Sen. John McCain (R-Ariz.). He also harangued his fellow Senate Republicans to support a moratorium on earmarks. Rep. Mick Mulvaney (R-S.C.), a conservative who said he considered DeMint a mentor, said the senator told him not to be co-opted in Washington. " "Be true to yourself," " Mulvaney said DeMint told him. "And he said, "You're going to have to try and figure out if you're going to fix this from within the system or without the system." " By "system," Mulvaney said, DeMint meant the Republican mainstream. With his Senate Conservatives Fund, a political action committee, DeMint raised money - $17.5 million in 2012 - for a string of long-shot conservative candidates, who often defeated mainstream Republicans in party primaries. DeMint's money helped create a new brand of Republican senator, focused, like DeMint, on shrinking the federal government, cutting spending and supporting conservative social causes. But in general elections, DeMint's people lost more often than they won. In 2010, he helped nominate three Republicans - Sharron Angle in Nevada, Christine O'Donnell in Delaware and Ken Buck in Colorado - for Senate seats that had seemed within reach. All three lost their races. In 2012, it happened again, with candidates Josh Mandel in Ohio and Richard Mourdock in Indiana losing to Democrats. These losses were cold comfort to Republicans whom DeMint had helped undermine before, such as former South Carolina congressman Bob Inglis. Inglis had been a friend of DeMint, but DeMint declined to endorse Inglis in a 2010 Republican primary fight against a former prosecutor, Trey Gowdy, whose politics were closer to DeMint's. That strategy may work in South Carolina, Inglis said Thursday, but it is dangerous to attempt on the national level. "We've got to get into the business of addition and multiplication, and out of the business of subtraction and multiplication," Inglis said. Because it ain't working out for us. The defeat of DeMint's allies this year helped Republicans remain the Senate minority and left DeMint with little trust from the Republican leadership. During DeMint's eight years in the Senate, none of the bills he has authored have been signed into law. "He hasn't been terribly successful as a politician or as a senator," said Mark Tompkins, a political science professor at the University of South Carolina who has followed DeMint's career. At the end of the day, he just wasn't temperamentally a man of the Senate. DeMint will move to head the Heritage Foundation, a place where he has deep ties. In fact, in 2009, the head of that think tank said of DeMint: He "may be the junior senator from South Carolina, but here we call him the senior senator from the Heritage Foundation."