GREENVILLE, S.C. (AP) — With his Republican rivals jockeying for victory in New Hampshire, presidential hopeful Fred Thompson sought Tuesday to increase up 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 supporters at a pancake house in the northern part of the state as he began a 11-day bus tour.

In November, one state poll had the former Tennessee senator in a virtual tie for the lead in South Carolina 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.

A New Hampshire poll out this week showed Thompson in low single-digits there. Analysts and even Thompson supporters say he must do well in the Jan. 19 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 for Thompson in Iowa, where he 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.

''It's going to be important, and I think the focus that we're giving to South Carolina is a good tell of just how important it is to us,'' Sadosky said Monday.