Update at 11:10 a.m. ET: With five precincts remaining, Assistant Attorney General JoAnne Kloppenburg has taken a 447-vote lead over incumbent Justice David Prosser in the Wisconsin state Supreme Court race out of 1.5 million votes cast, the AP reports.

Update at 10:50 a.m. ET: With 10 precincts remaining, Assistant Attorney General JoAnne Kloppenburg has taken a very narrow lead over incumbent Justice David Prosser in the hard-fought Wisconsin state Supreme Court race.

As of 10:30 a.m. ET, the Associated Press reports that Kloppenburg has taken a 140 vote lead after all but 10 of the state's 3,630 precincts have been counted.

A recount seems likely, regardless of the final tally.

Earlier posting: The Wisconsin Supreme Court election that has turned into a proxy battle over the union-curbing policies of Republican Gov. Scott Walker is too close to call. The conservative-leaning incumbent is a few hundred votes ahead of a little-known challenger backed by unions.

After 99% of the vote is in, Justice David Prosser has a lead of a few hundred votes over JoAnne Kloppenburg, assistant attorney general.

The Associated Press, which said the race was too close to call, reports that it could take hours to get the final votes counted. In any case, the AP reports, the race probably will face a recount, the Associated Press reports.

Kloppenburg turned an uphill fight against Prosser into a tight battle after the political uproar over Gov. Walker's divisive move to curb the collective bargaining rights of public service employees.

Although officially non-partisan, the seven-person court is split 3-3 between liberals and conservatives. The winner of the election could determine the fate of the union law.

Her allies have presented Kloppenburg, 57, as an alternative that would tilt the court's ideological balance to the left.

Prosser, 68, has told the AP that he doesn't necessarily agree with Walker's law, but angry Democrats have portrayed him as a Walker clone.

That changed the dynamic of the race. Prosser handily won a non-partisan February primary with 55% of the vote, while Kloppenburg finished second out of four candidates with 28%.

Walker has said he wouldn't interpret the election results as either an endorsement or indictment of his policies, the AP reports.