WASHINGTON — In typical blunt fashion, U.S. Sen. Jim DeMint, R-S.C., recently warned of the dangers to America from the lame-duck zombie Congress that is poised to resolve weighty issues, such as the looming “fiscal cliff,” before it adjourns at the end of the year.

The biggest threat is “the ‘lame duck’ members of Congress . . . who have either announced their retirement or been replaced by voters,” DeMint wrote last month on his senatorial website blog. “These few dozen ‘zombie’ legislators, unlike their colleagues, are utterly free from public accountability.”

With his impending departure from the Senate announced Thursday, the South Carolina Republican officially joined the zombie class. His 14-year congressional career ends when the 112th Congress completes its business.

But the S.C. conservative firebrand won’t be roaming the political countryside. From his new perch at the Heritage Foundation, he very likely will continue the role he carved during his days in the Senate and House of Representatives as a cultivator and kingmaker of conservative congressional and presidential candidates — and occasional irritant to his party.

“South Carolina has a long tradition of colorful politicians who stand outside the mainstream,” said Blease Graham, an emeritus University of South Carolina political science professor, harking back to the late Strom Thurmond and bare-knuckle political guru Lee Atwater. “DeMint stands to take a place among that group.”

Since DeMint’s arrival on Capitol Hill, when he was first elected to the House in 1998 and the Senate in 2004, he has been a drum major for fiscal restraint and conservative purity within the Republican Party in terms of policy and candidates.

DeMint’s star first rose around 2006, when he spearheaded the cause against targeted political spending known as earmarks, helped scuttle a drive for comprehensive immigration legislation sought by then-President George W. Bush and, later, led the charge against President Barack Obama’s health-care law.

The soft-spoken DeMint used skills he developed as the former owner of a marketing firm to deftly label his targets. Comprehensive immigration became “amnesty” and he warned — incorrectly, as it turned out — the battle over the health-care law would be Obama’s “Waterloo.”

One of the poorest members of Congress — with an estimated $40,501 in wealth, according to a Washington Post analysis of lawmakers —DeMint used his Senate Conservatives Fund political action committee to contribute heavily to Tea Party and other conservative candidates. The PAC amassed millions of dollars, and much of it went to political unknowns or novices, or to those whom the traditional Republican Party establishment had rebuffed.

Some of DeMint’s political children paid homage Thursday.

“He created the opportunity for principled but underfunded candidates to have a chance,” said U.S. Sen. Marco Rubio, R-Fla., mentioned as a possible vice-presidential candidate this year and a potential presidential contender in 2016. “That was certainly my case. So I think the Republican conference is better for Jim DeMint’s service.”

But not all Republicans agree.

DeMint often was at loggerheads with the party’s election apparatus, which more often than not was looking for House and Senate candidates with the best chances of winning and leading the party to a congressional majority, instead of which candidates were more conservatively pure.

“The priority is not first the majority,” DeMint said in 2010. “We had a big majority with 55 Republican senators. We had a big House majority. We had Bush in the White House. We spent too much, borrowed too much — and they (the voters) threw us out.”

Even on his way out of office, DeMint thumbed his nose at Republican House Speaker John Boehner this week for his counterproposal to Obama to avert the fiscal cliff.

“Speaker Boehner’s $800 billion tax hike will destroy American jobs and allow politicians in Washington to spend even more, while not reducing our $16 trillion debt by a single penny,” he said. “This isn’t rocket science.”

DeMint and fellow Republican U.S. Sen. John Cornyn of Texas, the chairman of the National Republican Senatorial Committee, argued over campaign tactics. Cornyn complained DeMint contributed to GOP defeats by inserting himself and his money into some races.

DeMint-backed candidates such as Rubio and Rand Paul of Kentucky, Mike Lee of Utah, Patrick Toomey of Pennsylvania and Ron Johnson of Wisconsin all won seats in the Senate.

But some Republicans complain DeMint cost the party winnable seats by throwing his support or resources to candidates such as Richard Mourdock, who failed to win the seat last month held by outgoing U.S. Sen. Richard Lugar, R-Ind., and Delaware’s Christine O’Donnell, who defeated moderate Republican Rep. Mike Castle in the 2010 primary for a Senate seat but was crushed by Democrat Chris Coons in the general election.