In the still-to-be-decided race for a US Senate seat in Minnesota, an Associated Press analysis of votes indicates that most ballots lacking a Senate vote were cast in counties won by Democrat Barack Obama.

The 25,000-vote difference in presidential and Senate race tallies could be due to different reasons - either some of the voters might have intentionally bypassed the Senate race, or others might have mismarked their ballot, or optical scanning machines might have misread them.

As such, a recount of the votes will begin November 19, and will use manual inspection to detect such ballots.

The AP finding could have implications for Republican Sen. Norm Coleman and Democrat Al Franken, who are separated by a very thin margin of a couple of hundred votes, or about 0.01 percent.

Three counties — Hennepin, Ramsey and St. Louis, which contain the population centers of Minneapolis, St. Paul and Duluth — account for 10,540 votes in the dropoff between the presidential race and the Senate race. Each saw Obama win with 63 percent or more of the vote.

A University of Minnesota political science professor, Larry Jacobs, said the AP analysis of the dropoff between the two races creates a “zone of uncertainty” that could become a focal point for the campaigns, adding that the numbers favor Franken.

Meanwhile, Coleman campaign manager, Cullen Sheehan, complained of “statistically dubious and improbable shifts that are overwhelmingly accruing to the benefit of Al Franken.”