Ramsey County officials say they've charged 28 people for illegally voting or registering to vote in the 2008 election and are investigating more than 180 more.
Phil Carruthers, director of the prosecution division of the Ramsey County Attorney's office, says the number of cases is somewhat higher than previous elections. He said it's impossible to say whether the illegal voting might have altered the outcome of the Senate race.
"It's total speculation. First of all so far only a limited number of people in fact have been charged with illegally voting so the number is very limited," Carruthers said. "And then of course we don't know who they would have voted for or did vote for, so it's total speculation."
Democrat Al Franken won the 2008 U.S. Senate race by 312 votes after a recount.
Dan McGrath, with the conservative group Minnesota Majority, says the findings shouldn't reverse the 2008 election but should raise concerns about future elections.
"That race is over. It's been decided. We have Sen. Franken and there's no changing that," he said. "What I'm concerned with is protecting the integrity of the upcoming election so that every voter knows confidently when they walk into the polling place that their vote is going to count and not be disenfranchised by illegitimate votes."
McGrath says requiring a photo id at the polls along with an electronic system to scan for felons is the best option to fix the system.
In Hennepin County, Deputy County Attorney Pat Diamond says authorities are investigating 216 allegations flagged by Minnesota Majority but have yet to charge anyone from that group.
(This report contains information from the Associated Press.)