

Professor Emeritus at Johns Hopkins School of Medicine Dr. BenCarson speaks at the 41st Annual Conservative Political Action Conference (CPAC, at the Gaylord National Resort and Convention Center in National Harbor, Maryland, USA, 08 March 2014. EPA/MICHAEL REYNOLDS)

The disconnect between social conservatives and the GOP has become a “chasm,” says evangelical leader Gary Bauer. The libertarian wing of the party is gaining steam and leaving values voters behind.

Enter Ben Carson.

The African American former surgeon became a sensation in conservative circles in 2013 after proclaiming Obamacare the “worst thing to happen to this nation since slavery.”

Carson, 62, has since built up a sizable media profile, thanks to his regular appearances on conservative news outlets. He came in third in the straw poll at this year’s Conservative Political Action Conference. He's on a national tour this month to promote his book “One Nation” — a title that has sold more copies than Hillary Rodham Clinton’s “Hard Choices.” He's announced his own political action committee. And a super PAC formed to draft him to run for president — look out for the “Run Ben Run!” bumper stickers — has brought in a very healthy $7.3 million haul so far this cycle.

But Carson, some evangelicals worry, is following a well-worn path for promising socially conservative contenders: to political stardom, grassroots support — and stinging defeat.

And so the buzz around him underscores the unsettled nature of the GOP’s social-conservative wing this time around: Even as he gains traction, some activists fear that evangelicals risk pouring time, money and hope into another doomed candidate.

Socially conservative outsiders running for the Republican presidential nod can tap into big potential advantages — starting with well-established and politically motivated grass-roots networks in early-voting primary states with large evangelical populations, such as Iowa and South Carolina. They tend to attract plenty of earned media. And their messages play well in retail environments -- the town halls and small-town stops that play an outsize role in these early contests.

But that's where the wheels tend to come off. As the presidential campaign moves on to larger states with more expensive media markets, politically inexperienced candidates such as Carson typically struggle to maintain momentum. The door prize for strong early showings is increased media scrutiny -- and many candidates find themselves wilting under this harsher brand of spotlight. The same loyal staffers who helped harness grass-roots energy early on often aren't savvy or experienced enough to establish a truly national infrastructure. Donations drop off. Campaigns sputter to a stop.

Even the most successful templates for a Carson presidential run have followed this model:

Pat Robertson, founder of the Christian Broadcasting Network and a former Southern Baptist minister, managed to come second in the Iowa caucuses against incumbent Vice President George H.W. Bush — but fared less well starting in New Hampshire.

Gary Bauer, the former Reagan adviser who now runs the Campaign for Working Families, topped the CPAC straw poll in 1999 but came in fourth in the Iowa caucuses, with just 8 percent of the vote.

Mike Huckabee and Rick Santorum stormed to strong early showings against Mitt Romney in successive cycles and held on for months — but couldn't make the transition to a more national race.

And, perhaps the closest analogue in terms of trajectory so far: Herman Cain, who also used a big speech — in his case, at the Faith and Freedom Conference — to grab social conservatives' hearts in 2012. His effort shuddered to a halt not long after sexual harassment allegations against him became public.

Beyond the question of which candidate will capture the evangelical imagination this cycle, there's a bigger, more existential conundrum nagging at the margins as 2016 approaches: how much does that vote still matter to the GOP?

Candidates such as Texas Gov. Rick Perry — who made a major play for the evangelical bloc during his first run — seem to be sidestepping or downplaying the importance of social issues this time around. Libertarians such as Kentucky Sen. Rand Paul are taking center stage. Poll after poll suggests rising support for social change like same-sex marriage and the legalization of marijuana — even, at a slower pace, within the evangelical community.

Plus, in the face of a potential return of the Clinton political juggernaut, the traditional tug-of-war between those who want to back the most ideologically pure candidates and those who want to back the most viable ones stands to swing solidly in favor of the pragmatists.

In short: 2016 is still a long way away. And Ben Carson may yet win the evangelical primary. But if the past is any precedent, it probably won't matter in the fall. And if the future shapes up as expected, his supporters may be in for an even more disappointing cycle than usual.