Sen. Jim DeMint appears to have closed the door on endorsing a candidate in the Republican presidential primary.

With South Carolina’s primary approaching on Saturday, DeMint today sent an email to his Palmetto State supporters announcing that he would not back a candidate in the race. DeMint had previously announced he would not endorse, but he had left the door open to changing his mind. The finality of DeMint’s language in today’s email closed the door.

“I do not have a favorite in this race and I will not endorse a candidate,” DeMint said.

In 2008, DeMint endorsed former Massachusetts Gov. Mitt Romney, who this month won Iowa and New Hampshire and has been leading in public opinion polls of South Carolina heading into Saturday’s primary. Although DeMint maintains a warm relationship with Romney, he has said previously that if he endorsed, he wanted to back a candidate who both had the backing of grass-roots conservatives and could be competitive in the general election against President Barack Obama.

Since 2008, DeMint’s popularity has skyrocketed in conservative circles — both in South Carolina and nationally, raising the stock of any endorsement he might offer in the 2012 contest. DeMint, who has supported and helped raise money for Republican Senate candidates backed by the tea party, initially said he would withhold his endorsement in the presidential race to help increase the competition for South Carolina’s delegates.

As speculation increased in recent days that he would ultimately endorse Romney despite repeatedly saying that he was going to focus on electing conservatives to the Senate, DeMint appears to have decided to address the issue bluntly.

“The presidential primary in South Carolina has intensified and my name is being thrown around a lot,” DeMint said in the email to supporters. “I have complimented several of our candidates when they spoke out on conservative issues, but the media has suggested that I favor one over the others. I’m writing today to make sure you know exactly where I stand.”

DeMint is not the only high-profile South Carolina Member who has not endorsed a presidential candidate. Sen. Lindsey Graham and freshman Rep. Tim Scott, a tea party favorite, also have yet to back a candidate. Both Members sounded noncommittal in Sunday morning television interviews. South Carolina Gov. Nikki Haley and state Treasurer Curtis Loftis, however, have endorsed Romney. Both Haley and Loftis were elected in 2010 with substantial tea party support.

Meanwhile, today Romney picked up another Congressional endorsement, this time from House Transportation and Infrastructure Chairman John Mica (R-Fla.). The former Massachusetts governor has received more Member endorsements than any of his competitors.