Edwards + Kucinich > 15%?

According to WHO TV in Des Moines, the Edwards and Kucinich campaigns have agreed to combine their caucus support if either candidate isn’t “viable” (meaning has less than 15% support). It’s not clear if this is a caucus-by-caucus plan or something they plan to coordinate statewide.
It’s also not clear what happens if both are below 15%: that is, which one gets the support then? This is a clue, though, that the Edwards people know that they don’t have to ground game to convert his last-minute surge in the polls into comparable caucus votes.