Democrats in Wisconsin were crying foul Friday after a significant vote-count change in the hotly contested Supreme Court election gave the conservative incumbent the lead in a race that could decide the fate of the state's new divisive collective bargaining law.

Waukesha County Clerk Kathy Nickolaus said it was "human error" that resulted in more than 14,000 votes from her predominantly GOP county not being reported on Tuesday. The corrected totals gave conservative Justice David Prosser a 7,500-vote lead, according to unofficial tallies, and undid the earlier likelihood of a recount.

Rep. Peter Barca, Democratic Assembly minority leader, said Nickolaus' revelation "raises disturbing questions, particularly in light of her partisan history."

"The new Supreme Court race vote totals she 'discovered' during canvassing not only swung the election but also put the race just barely past the amount needed to trigger a state-financed recount," he said in a statement.

"It doesn't instill confidence in her competence or integrity," he said, adding that the mistake could warrant an investigation.

Liberal groups also howled in protest.

"There is a history of secrecy and partisanship surrounding the Waukesha county clerk and there remain unanswered questions," Scot Ross, director of the liberal group One Wisconsin Now, said in a statement.

But Republican state Senate Majority Leader Scott Fitzgerald told Fox News he believes Nickolaus made a mistake.

"The canvas process in Wisconsin is pretty routine after an election happens," he said, "and, in the many that I have been involved in over the years, certainly there are changes to the vote totals that come in on election night."

Fitzgerald noted that Grant County had added more than 100 votes for challenger JoAnne Kloppenberg after the initial count.

Prosser had faced a surprisingly strong challenge from Kloppenburg, a little-known assistant state attorney general who drew last-minute support -- and significant get-out-the-vote efforts -- from opponents of Gov. Scott Walker's push to limit union power as part of a budget-balancing plan.

"I like to think that I have survived a nuclear firestorm of criticism and attack and smear," Prosser told Fox News Thursday night. "As far as I'm concerned, if these results hold up, I will be the winner."

Prosser added that he is waiting out the process.

"I'm not conceding, and I'm not congratulating. And I'm not claiming victory," he said.

Prosser said the race should not be considered a referendum on Walker or any legislation that may end up at the court.

The fate of that law, which is facing legal challenges, could end up before the state Supreme Court, where Prosser or Kloppenberg could tip the balance. On Thursday, the state attorney general sought expedited review from the state's high court.

Opponents of the law had hoped a Kloppenburg victory would set the stage for the high court to strike it down.

Fitzgerald said he didn't want to predict the outcome of  the law regardless of who's in the justice's seat, but he would be pleased if Prosser held the post.

"I wouldn't want to make any presumptions on what the Supreme Court might do. But, certainly, I think, you know, having Justice Prosser there, I think he has been a strong voice for the law, and a strong voice for Wisconsin for many, many years, and, I obviously, I'm certainly hopeful that the vote totals hold up for Justice Prosser, after the canvas is completed," he said.

Nickolaus apologized Thursday for the error, saying the most significant error occurred when she entered but did not save totals from the city of Brookfield, a suburb of Milwaukee.

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

Kloppenburg's campaign manager, Melissa Mulliken, demanded a full explanation of how the error occurred and said an open records request for all relevant documents would be filed.

Ramona Kitzinger, the vice chair of Waukesha County Democratic party who observed the canvass, said she is satisfied the numbers are now correct.

"We went over everything and made sure all the numbers jibed up and they did," she said.

The Government Accountability Board, which is in charge of overseeing Wisconsin's elections, will review Waukesha County's numbers to verify the totals, said agency director Kevin Kennedy.

Kennedy said it was unfortunate the clerk didn't double-check the data before releasing it to the media. Kennedy also said such mistakes are known to happen but that "we just don't see them of this magnitude."

Nickolaus has faced criticism before for her handling of elections and previously worked 13 years for a state GOP caucus that was controlled by Prosser when he was Assembly speaker in 1995 and 1996. She was given immunity from prosecution in a 2002 criminal investigation into illegal activity by members of the caucus where she worked as a data analyst and computer specialist.

The corruption probe took down five legislative leaders, all of whom reached plea deals. Nickolaus resigned from her state job in 2002 just before launching her county clerk campaign.

Nickolaus also has been criticized by the Waukesha County Board for her handling of past elections and lack of oversight in her operations.

An audit of Nickolaus' handling of the 2010 election found she needed to take steps to improve security and backup procedures, including not sharing passwords. The audit was requested after the county's director of administration said Nickolaus had been uncooperative with attempts to have county experts review her systems and confirm backups were in place.

The Associated Press contributed to this report.