The Associated Press took a look at ballots for which scanning machines registered a vote for president and not for U.S. senator, making the case that of the approximately 25,000 such ballots, 10,000 are in Democrat Al Franken’s stronghold counties of Hennepin, Ramsey and St. Louis.

“These numbers present a roadmap for a Franken challenge,” University of Minnesota political science professor Larry Jacobs told the AP. “It suggests there are about 10,000 votes in the largest Democratic counties that are potentially going to tilt in Franken’s direction.”

The report also said that 18,000 of those ballots were in counties that went for Democrat Barack Obama for president, but the report doesn’t mention a significant number of split-ticket voters in this election, with voters supporting Franken’s opponents, Republican Norm Coleman or independent Dean Barkley, as well as Obama on the same ballot.

The margin between Coleman and Franken currently has a shrinking Coleman lead of 221 votes, well within the margin to trigger an automatic recount. A hand recount would spot ballots where voters indicated support for a Senate candidate, but did not fill in the oval clearly enough for the machine to register the vote or where the machine malfunctioned (See MnIndy’s report on potential scanning machine malfunctions). It’s also possible that voters intentionally skipped voting for a Senate candidate, as the scanners do not refuse to register a ballot with questions left blank, only ballots that contain overvotes.