A group that has challenged instant-runoff voting and other election issues filed suit Tuesday alleging that state and local elections officials do not properly determine the eligibility of voters who register at the polls on Election Day.

The group, the Minnesota Voters Alliance, was joined in the lawsuit by a group known as the Minnesota Freedom Council and by state Rep. Sondra Erickson, R-Princeton, who questioned whether the eligibility issue affected her close loss in 2008.

The lawsuit, filed in federal court, raises several issues relating to the integrity of Minnesota elections, including voting by felons and by people who have been determined to be mentally incompetent. But a key issue concerns Minnesota's same-day registration law and how election officials verify information submitted by those who register on Election Day.

The lawsuit argues that under the state Constitution, a person cannot be allowed to vote until his or her eligibility has been confirmed, said Andy Cilek of the Voters Alliance and the group's attorney, Eric Kaardal. But for those who register on Election Day, eligibility is not confirmed until after they vote, if at all, the group said.

Cilek said a photo ID system, such as is being debated at the Capitol, could "fix all these problems, and then some." He also said if the state allowed "provisional ballots," in which people's vote is not counted until they prove identity, that would also help.

A spokesman for Minnesota Secretary of State Mark Ritchie, the state's chief elections officer and a defendant in the suit, said it is reviewing the lawsuit but declined to comment.

Rep. Erickson told the news conference that the treatment of same-day registrants raises questions about her 89-vote loss to Gail Jackson in 2008. The lawsuit says there were 4,044 same-day registrations in the race, "all of which were unconfirmed on election day when their ballots were counted." Even after the election, the lawsuit says, the state and counties were "unable to confirm" the qualifications of 242 voters who registered on Election Day.

Erickson won her seat back in 2010, defeating Jackson by 1,851 votes, and said she intends to run again this year.

She said she does not know if the treatment of same-day registrations affected the outcome of her race, but said she is concerned with "the integrity of our election system."