David Weigel at Slate filed a report over the weekend at the Values Voter conference in Washington, DC:

Inside the Omni Shoreham [hotel], there is no real anti-Cain agitprop, but there is an unhelpful one-pager at the National Organization for Marriage booth which informs people how candidates have answered the 2012 Pro-Marriage Presidential Pledge. This is the one that commits candidates to establish a special commission to investigate crimes against gay marriage opponents, among other things. And it tells us that Gingrich, Paul, and Cain have NOT signed the pledge. Will he "advance legislation to return to the people of the District"? UNKNOWN. Will he support a federal marriage amendment? NO.

I met two conference attendees, Larry and Lois Gladfeiler, who said they'd learned this, then [had] seen Santorum speak, and moved their allegiance accordingly.