People make donations to the Orange County Liberty Counsel after an event with Republican presidential candidate, former Speaker of the House Newt Gingrich (R-GA) at the Aloma Baptist Church Jan. 28, 2012 in Winter Park, Fla. - 

Jeremy Hobson: Leading up to last night's victory in Florida, Mitt Romney and his allies outspent Newt Gingrich and his allies by a margin of 5 to 1. When I say allies, I'm talking about super PACs -- independent groups that are allowed to spend unlimited cash as long as they reveal where the money's coming from.

But as our Washington bureau chief John Dimsdale reports, even the required disclosures make it hard to figure out who's making the donations.

John Dimsdale: Last year, Mitt Romney’s super PAC reported a $1 million donation from a company called W Spann. The trouble is, W Spann had disappeared and no one could tell where the money came from.

Bill Allison is the editorial director of the Sunlight Foundation, which promotes government transparency. He says some corporations are hard to trace.

Bill Allison: Sometimes all you have is the lawyer or accountant who filed the paperwork. You really don’t know who the interests are behind it. That’s what makes it so difficult to really follow the money in this election.

Eventually, a former colleague of Mitt Romney’s from Bain Capital claimed ownership of the $1 million donation.

Peter Stone: It’s very possible we’ll see some more cases of it this time around.

Peter Stone covers money and politics for the Center for Public Integrity.

Peter Stone: There’s some people out there who are probably a little nervous about being publicly identified with campaigns and we’re going to have to look very hard to see if we can dig up other cases like this. 

From now through Election Day, super PACs must disclose their donors every month.

In Washington, I'm John Dimsdale for Marketplace.