An Iowa conservative leader said Thursday he's not backing off a social-issues pledge put forth by his organization, saying it's not good enough for GOP presidential candidates to voice support for its principles but decline to sign it.

Bob Vander Plaats, the president and CEO of The Family Leader, wouldn't categorically rule out endorsing the bevy of Republicans who have declined to sign "The Marriage Vow," but "would categorically look at" backing Rep. Michele Bachmann (R-Minn.) and former Sen. Rick Santorum (R-Pa.), the vow's two signatories.

"The vow still remains," Vander Plaats said in a brief phone interview. "We're still standing by that. We want the candidates to sign the pledge. And that qualifies as an opportunity to get our endorsements."

The pledge was unveiled last week as a way to gauge possible endorsements or recommendations for GOP presidential candidates in the Hawkeye State. Bachmann and Santorum quickly signed, although the pledge included a controversial provision — that has since been stricken — suggesting that African-American families were healthier under slavery than in contemporary society.

"Right now there's two that we would categorically look at for endorsing, Rick Santorum and Michele Bachmann," Vander Plaats said.

That provision, along with some of the pledge's more deeply conservative elements, led a number of candidates to refuse to sign it. Former Massachusetts Gov. Mitt Romney's (R) campaign called elements of the pledge "undignified and inappropriate," while candidates like former Minnesota Gov. Tim Pawlenty (R) and businessman Herman Cain voiced support for the vow's principles, but ultimately declined to sign it.

"You get a guy like Mitt Romney — the vow, quite frankly, a lot of it was to get a guy like Gov. Romney on record," Vander Plaats said of the former Massachusetts governor, who hasn't made Iowa a priority of his campaign.

Rep. Ron Paul (R-Texas) and former House Speaker Newt Gingrich (R-Ga.) have opted not to sign, and former Utah Gov. Jon Huntsman (R) has said he won't sign any pledges.

Vander Plaats said it's possible that he and his organization might not endorse or recommend any candidate. The decision will come after a candidate debate on Nov. 19, and months' worth of candidate gatherings in Iowa.

Of course, there's also the matter of late entries by candidates — think former Alaska Gov. Sarah Palin (R) or Texas Gov. Rick Perry (R) — who could alter the dynamic of the campaign in Iowa.

Vander Plaats said he met Palin briefly at the screening of a biographic movie about her in Pella, Iowa, but not long enough to make much conversation.

As for Perry? Vander Plaats said the Texas governor left him a voice mail recently, but that the two haven't spoken directly yet.