On the ground in Iowa, Jonathan Martin is reporting:

CEDAR RAPIDS, Iowa -- Mitt Romney said he would extend "the benefit of the doubt" to Rudy Giuliani over charges that the former mayor billed security expenses to obscure city agencies -- but also suggested that he welcomed the story playing out further.

"This is something that the mayor is addressing," Romney said at a press availability after a town hall forum at a community college here. "And I think we ought to give him the opportunity to address that as he feels appropriate. Let him have an ample chance to look at the history and explain what he feels is needed."

Giuliani "hasn't really laid out at this stage his full explanation or all that was shown," Romney continued. "So my view is, let's give the benefit of the doubt until he has a chance to do that."