CHARLESTON, S.C. - In her quest to win the White House, Michele Bachmann needs voters like Barbara Bates more than ever.

Bates is a fervent Tea Party member on the crucial GOP turf of South Carolina, where Bachmann is working to extend her Midwestern Bible Belt appeal.

Bates and her husband, retirees in the coastal community of Goose Creek, have been paying very close attention to the GOP presidential field this summer. They have been regulars at many of the Palmetto State's big GOP gatherings, including Texas Gov. Rick Perry's presidential announcement on Aug. 13 and at least two of Bachmann's recent town halls.

"I have not heard her say anything that I disagree with," Bates said. But she and her husband, Bill, retired from the Navy, are still up for grabs, with Perry tugging at the loyalties of their deeply conservative hearts.

How to decide? "Electability is going to have to factor into it," Bates said.

With Perry surging in South Carolina, Bachmann is struggling to lay the foundation of a national campaign that can compete for money and resources with two of the GOP's top candidates -- Perry and former Massachusetts Gov. Mitt Romney.

Florida and other big states loom large, but South Carolina appears to be the firewall where Bachmann must lay to rest the questions about whether her campaign can go all the way. Those questions have intensified with the entrance of Perry, who matches Bachmann's faith-centered, small-government politics, with an added measure of executive experience to boot.

"The early stage of the campaign is the party checking out the ideological credentials of their candidates," said former U.S. Rep. Vin Weber from Minnesota, who switched over to Romney after helping former Gov. Tim Pawlenty's now-defunct presidential campaign get going. "But as you move forward in the process, questions of electability and plausibility as president loom a little bit larger."

That is particularly true for South Carolina voters, who have a knack for picking the eventual winner in GOP nominating contests going back to 1980, when Ronald Reagan was elected president.

They're also deeply conservative and heavily evangelical, much like their counterparts in Iowa. After Bachmann won the straw poll in Ames, Iowa, on Aug. 13, she immediately set a course for South Carolina, where Perry was launching his presidential bid.

With the early voting states of Iowa and South Carolina arguably within reach for Bachmann, her strategists have long hoped that she might be able to claim two of the first four contests, easing pressure to do well in the Romney strongholds of New Hampshire and Nevada.

Bachmann has not been to New Hampshire since Ames. For her, it seems, South Carolina is the new Iowa.

The Perry challenge

South Carolina also happens to be a critical state for Perry, who has been playing on the affections of fellow Southerners who see in him as a kindred spirit with a superior organizational and fundraising network.

"I would assume if I'm Rick Perry, I need to win South Carolina," said Des Moines attorney Jeff Courter, who voted for Perry in the Ames Straw Poll. "Perry needs to beat Bachmann first to have a straight shot at Romney, though quite frankly, Perry has moved past Romney."

It appears Perry has moved past Bachmann as well. A Public Policy Polling survey released this week gives Perry a 20-point lead in South Carolina, leading Romney 36 percent to 16 percent. Bachmann is now third at 13 percent.

Among Republicans who describe themselves as "very conservative," which is the largest segment of the GOP electorate in South Carolina, Perry's at 44 percent to 14 percent for Bachmann, with Romney trailing at 9 percent.

"When push comes to shove, I think it's going to be Perry and Bachmann in South Carolina," said Tim Callanan, chairman of the GOP Party in Berkeley County, outside Charleston.

One reason is that South Carolinians have not seen much of Romney, raising questions about how hard he will fight there. Another is that he's off the list for many ardent religious conservatives such as Bates.

"He was never on my list," Bates said of Romney.

That sentiment would seem to open up some space for Bachmann, who has toned down some of the incendiary rhetoric that raised her national profile in Congress. But some locals say it is not that simple.

"This is as Republican as it gets," said Columbia, S.C., attorney Henry McMaster, a former state attorney general and GOP chief. "But it's a mature Republican state. People are practical here."

That means that there's still a strong establishment streak in South Carolina. With its first-in-the-South primary, South Carolina shattered the hopes of GOP mavericks John McCain in 2000 and Mike Huckabee in 2008.

'Emotional choice'

With Perry now eating rapidly into Bachmann's support, Bachmann may have reached a brief zenith in Iowa.

"If you look at Michele Bachmann's polling, she's an emotional choice," said Charleston GOP strategist Jim Dyke, a veteran of four presidential campaigns. "Usually the emotion is pretty much shaken out of the race by South Carolina."

Dyke also is skeptical about Bachmann's chances in Iowa, where some polls now give Perry the lead. Despite Bachmann's straw poll win, Dyke said, "there's zero certainty she will win Iowa" in the first-in-the nation caucuses in February.

Meanwhile, McMaster says that the main unifying principle in South Carolina is finding the candidate with the best chance of beating President Obama in 2012.

To McMaster, that favors former Utah Gov. Jon Huntsman, who has been quoted saying the rest of the GOP field is too far to the right. "You can't run just by appealing to the people who go to the meetings with you," McMaster said.

But centrist appeal does not appear to be winning the day in South Carolina, and the central hurdle facing Bachmann is that Perry comes from the right, not the center.

U.S. Rep. Tim Scott of South Carolina, who introduced Bachmann at her town hall forum in Charleston, praised her as a politician who "started on the right, stayed on the right, and is still right."

But activists such as Bates still want someone who will do right in a general election: "I'm just going to have to listen to what they all say and make a determination from there," she said.

Kevin Diaz is a correspondent in the Star Tribune Washington Bureau.