That close margin had political insiders from both sides talking about the possibility of a recount, which Wisconsin has avoided in statewide races in recent decades. Any recount could be followed by lawsuits - litigation that potentially would be decided by the high court.

The razor-thin result was the latest twist in Wisconsin's ongoing political turmoil. The state has drawn the attention of the nation in recent weeks because of the fight over a controversial law sharply restricting public employee unions, which caused massive weeks-long protests in the Capitol, a boycott of the Senate by Democrats and attempts to recall senators from both parties.

Interest groups on both sides had portrayed the election as a referendum on Gov. Scott Walker's agenda and particularly on the collective bargaining law. Conservatives backed Prosser, and liberals supported Kloppenburg, even though the candidates themselves insisted they were politically neutral.

Legal challenges to the new law - which would eliminate most collective bargaining for most public employees - are expected to reach the high court, but it's not clear if the justices would take up the case before this race's winner is scheduled to be sworn in Aug. 1.

 
Thomas Lifson adds:

Incumbent  Justice David Prosser holds a 585 vote lead as of 10 AM EDT, with 99% of precincts reporting this morning. The race is regarded as critical to union efforts to overturn the state's new labor union laws protecting  workers against forced collection of union dues, and as Rick noted, unions poured in money and manpower. It is clear that the aroused citizenry of Wisconsin was not about to let the unions triumph.

Turnout was high, Ben Jones of USA Today:

Residents across the state flooded into polling stations to express strong opinions about Walker's policy initiatives. The voters helped boost turnout in many places to twice the level of a typical spring election, sending some clerks scrambling for extra ballots.

Unless the final precincts to report are heavily pro-Kloppenburg (as has happened in  Washington State, Minnesota, and elsewhere, with newly "discovered" votes tipping an election to the Democrat), Prosser will eke out a victory. According to Jones:

Under Wisconsin election law, a candidate has three days after the official results have been tallied to request a recount. The candidate must specify a reason for the request, such as a belief a mistake was made in the counting or some other irregularity.

Should Kloppenburg magically come up with a ballot box stuffed votes for her, and end up like Al Franken, a victor under suspicious circumstances, she will face a serious challenge to her sitting in judgment on the state's newly passed labor relations law. Ann Althouse, a professor at the University of Wisconsin Law School notes that her campaign signs indicate that she has already made up her mind on the law, and therefore must recuse herself:

Update from Richard Baehr:

Kloppenberg has taken the lead, now 140.  Ten precincts left (out of 3630), and all but 1 are in counties she won. It is a huge advantage to head into a recount as the candidate with the lead, especially in a "good government" state like Wisconsin, with a GOP governor who has reviled by most of the state and national media.  Kloppenberg lead is now almost 447 with 5 precincts left.  2 of the 5 are in Milwaukee County, and unless they are suburban precincts, Prosser will lose. 

Counties with big Democrtic advantage have slowly announced the  the last precincts released during the night and early morning -- shades of Illinois presidential race in 1960 (how many votes do we need?).

Update from Richard Baehr:

As of noon EDT, the Kloppenburg lead is 224, and still 3 precincts out -- two in Milwaukee County, which should be god for Kloppenburg unless they are suburban precints, and one in Jefferson, a good GOP county (which might give Prosser 100 vote margin). It is likely, I think, she will have a small edge going into the recount (less than 500) unless the remaining 2 precincts in Milwaukee County are from the inner city, which would give her more of a boost.

Why does it take over 12 hours to report results from a precinct?  There were a 100 not reporting hours after polls closed.

Update:

The missing precinct is Lake Mills.  If it goes 2 to 1 for Prosser, we could  have a tie (700-760 votes estimated to be left with Kloppenburg ahead by 235). Jefferson County  went 4 to 3 for Prosser.

Update:

Polls are all in. Kloppenburg wins by 204 votes.