GREENVILLE, S.C. — With his Republican rivals jockeying for victory in New Hampshire, presidential hopeful Fred Thompson sought Tuesday to boost his support in this early voting state considered critical to his campaign.

"I don't know of any better place to stand my ground and test my case than in South Carolina," Thompson told a couple of hundred people at a pancake house in the northern part of the state as he began an 11-day bus tour.

He said the results in New Hampshire and in Michigan on Jan. 15 will factor into whether he stays in the race, but that South Carolina will be key.

Arizona Sen. John McCain won the Republican primary in New Hampshire.

"This is where we make our stand — this is where I have chosen to make my stand," Thompson told a crowd at a barbecue restaurant. He later told reporters he needs to do well in South Carolina, which votes Jan. 19.

"There's no question about it. It could prove at the end of the day that South Carolina is determinative as far as I'm concerned, but we're not there yet," he said.

Thompson said he didn't expect to win New Hampshire, but went there to participate in two weekend debates.

"It's been about getting to South Carolina the whole time. South Carolina is the gateway to the rest of the country," Thompson told Fox News Channel in an interview Tuesday night. "These elections are not decided in two or three locations. They're decided in the rest of the country in the South and the West, and the rest of the Midwest gets to participate, too.

"It's been all about getting here and this has got to be considered my firewall," he continued. "I've got to do very well here if not win here. And, you know, there's no question about that. And I will stake my ground in South Carolina."

In November, one state poll had the former Tennessee senator in a virtual tie for the lead with former New York Mayor Rudy Giuliani and former Massachusetts Gov. Mitt Romney. A month later, eventual Iowa caucus winner Mike Huckabee came on strong, leading or sharing the top spot in three other surveys.

Analysts and even Thompson supporters say he must do well in the Republican primary here to continue a viable campaign through Feb. 5, when more than 20 states hold primaries or caucuses.

"If he does not do well here, it's pretty much over," said South Carolina state Sen. Larry Grooms, a regional chairman for the campaign.

The urgency is not lost on either the candidate or his backers. On Tuesday, Thompson supporter Chris Rush asked the candidate how to gain more media attention.

"Win South Carolina," Thompson shot back.

The bus tour strategy worked well in Iowa, where Thompson finished ahead of the fourth- or fifth-place slot that had been predicted, said Thompson campaign spokesman Jeff Sadosky. A good finish in South Carolina, Sadosky said, could help boost Thompson's prospects on Feb. 5.

Recent polls in South Carolina show Huckabee leading, with Thompson's support tough to read. He placed second in one survey; in two others, he placed fourth and fifth.

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Associated Press writer Meg Kinnard in Columbia, S.C., contributed to this report.