WASHINGTON (Legal Newsline) -- Wisconsin Congresswoman Tammy Baldwin sent a letter Friday to U.S. Attorney General Eric Holder asking for a federal investigation into the "questionable handling" of votes in her state's Supreme Court race.

On Thursday, Waukesha County Clerk Kathy Nickolaus revealed that she incorrectly entered vote totals in the state's hotly contested high court race.

According to unofficial tallies, the incumbent Justice David Prosser now has a 7,500-vote lead over opponent JoAnne Kloppenburg.

As of 4 p.m. Wednesday, a final, unofficial vote count had showed Kloppenburg, the state's assistant attorney general, with 204 more votes than Prosser.

The city of Brookfield sent its results to Nickolaus, who reportedly put them in the system but forgot to save the data. She later discovered her mistake and added the missing votes again.

"This is not a case of extra votes or extra ballots being found," Nickolaus said last week. "This is human error, which I apologize for."

Nickolaus is reportedly a Republican, has worked for a state GOP caucus that was once controlled by Prosser, and has previously faced criticism for her handling of elections.

Baldwin, a Democrat, wrote Holder, "Following this week's election for the Wisconsin Supreme Court, numerous constituents have contacted me expressing serious doubt that this election was a free and fair one. They fear, as I do, that political interests are manipulating the results."

"To assure public confidence in our democratic election process and guarantee that votes are fairly counted and reported," Baldwin asked Holder to assign the Justice Department Public Integrity Section, which oversees the federal prosecution of election crimes, to investigate the matter.

Justice Department spokesman Wyn Hornbuckle told Fox News in an e-mail Saturday that the department would review the letter. He declined to comment further.

Prosser has sat on the Court since 1998. Kloppenburg has worked as a litigator and prosecutor with the state Department of Justice since 1989.

Though the race is nonpartisan, Prosser is part of the conservative majority on the Court. A Kloppenburg win most likely would have tilted the Court to the left. Her taking the seat also might have impacted the ongoing legal challenge to Gov. Scott Walker's Budget Repair Bill.

The bill has been a source of controversy for months now, eliminating nearly all collective bargaining rights for those public employee union members. The Republican governor had proposed the bill in response to state budget deficits.

Nearly 1.5 million votes were cast in the race.

From Legal Newsline: Reach Jessica Karmasek by e-mail at jessica@legalnewsline.com.