DES MOINES -- Three leading evangelicals this morning held a conference call with pastors from around Iowa urging them to help turn their congregants out for the caucuses, Marc Ambinder reports. Tim LaHaye, author of the popular "Left Behind" series, Rick Scarborough and Michael Farris, a top advocate of home schooling, spoke with participants under the auspices of the US Pastor Council and Vision America.

The three are urging pastors to make sure their flocks are involved, though they cannot legally advocate on behalf of a candidate. Still, all three are backing Mike Huckabee, and their message is clear. "Pastors, we have a solemn duty to assure that our congregants are informed and then participate in this vital act of civic ministry through the caucuses," an email inviting pastors to call in reads.

With significantly fewer resources than Mitt Romney and other leading Republicans, Huckabee has to rely on surrogates to help boost turnout, a crucial component of any Iowa campaign. Pastors around the state have been key in Huckabee's rise in recent polls, and his continued strong performance rests largely on their efforts.