DES MOINES, Iowa — Rick Perry's poll numbers have held up despite Rick Santorum's rise, but social conservatives who make up Perry's base may jump to Santorum because of they see him as their best hope to nominate one of their own, say some experts in the state.

"There are a lot of people who like Perry but may ultimately vote differently," said Craig Robinson, a former political director of the Iowa Republican Party. "I can see how someone will say 'I really like Rick Perry but it doesn't look like it’s going to happen for him so I’m going to back someone who has the chance to win.' "

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Perry is in fourth place, according to the final Des Moines Register poll. His support actually jumped to 11 percent in the final up from 6 percent in their last poll a month ago, following a deluge of television advertising from the candidate. But Perry was in fifth place in the poll and Santorum clearly has the momentum right now.

Many of the socially conservative voters who are looking for an alternative to Mitt Romney have left Newt Gingrich and Michele BachmannMichele Marie BachmannBoehner says he voted for Trump, didn't push back on election claims because he's retired Boehner: Trump 'stepped all over their loyalty' by lying to followers Boehner finally calls it as he sees it MORE, and the remainder may reconsider their support of Rick Perry if they decide Santorum has the best chance to win.

If Perry can hold on to his current backers and build on that support in the final days leading up to the Jan. 3 caucuses, that narrows the chances Santorum has of winning in the state since they draw from the same general voter base. But if social conservatives who like both candidates decide Perry can't win, they may move towards Santorum — and the Des Moines Register poll's results are a hot topic of conversation at churches across the state Sunday morning, according to observers in the state.

The candidate recognizes this: He's been slamming Santorum on the campaign trail and in ads for seeking earmarks while he was in Congress. But some of his voters may decide it's too late for their favorite candidate, and instead back Santorum.

Perry ignored a question from The Hill while heading into a church near Des Moines Sunday morning, and had no public events scheduled in the state on the day. Santorum will barnstorm through conservative northwest Iowa Sunday afternoon.

Self-identified evangelical Christians make up approximately 60 percent of GOP caucus-goers in Iowa. They have moved from candidate to candidate this year, but have not coalesced for long around one. Santorum's late surge may mean he can lock up enough of them in the closing days of the campaign to pull off an upset win in the state.

Niall Stanage contributed to this story.