Wisconsin Republican Governor Scott Walker faces a recall vote on Tuesday over a law he championed to reduce the power of public sector unions in the state.
Here are five questions and answers about the unusual recall:
Q: What is a recall election and why is it being held?
A number of states have laws allowing an office holder to be removed during a term in extraordinary circumstances.
Only twice before in U.S. history has a governor of a state been recalled -- Lynn Frazier in North Dakota in 1921 and Gray Davis of California in 2003, according to the National Conference of State Legislatures.
After Walker won the 2010 election and Republicans won majorities in the Wisconsin legislature, he infuriated Democrats and labor unions by pushing through legislature to curb the power of public sector unions in the state.
Wisconsin has a strong history of a unionized workforce. It is home to a number of manufacturers, including iconic motorcycle company Harley Davidson, and was the first state in the nation to allow collective bargaining for state and local government workers in 1959.
Democrats in Wisconsin amassed nearly 1 million signatures on petitions from an adult population of 4.4 million over a 60-day period, almost double the number needed to force a special recall election for the governor.
Q: Why so much attention on a dispute in Wisconsin?
Three reasons: The outcome could tell a lot about the state of the labor movement in the United States; it could provide clues as to the political mood in a battleground state before the November election; and it gives both major political parties a chance to test their get-out-the-vote efforts before November.
On the labor movement, state and local governments in the U.S. face a major problem of unfunded pension plans and retiree benefits. Since the 2010 Republican sweep in congressional and state elections, some Republicans have accused the public sector unions of holding local governments hostage because they can, in effect, elect their bosses in government.
Wisconsin's Walker was the first of these conservatives to directly take on the unions and legislate away much of their power to collectively bargain. He said this was needed to balance the state budget.
His survival could encourage like-minded states to follow. Weakening the unions would be a blow to the Democratic party, which is dependent on unions for funding. Recall of Walker would be a warning to other states not to attempt what labor officials refer to as "union busting."
President Barack Obama won Wisconsin in 2008 comfortably and most political analysts had already put the state in his column again for 2012. If Walker wins, it could embolden Republicans to try to beat Obama in Wisconsin, at least forcing the president to campaign there and spend money.
Super PACs, the unregulated third party political fundraising groups, have poured money into Wisconsin, mostly on the side of Walker. If he survives they will be encouraged to use the same strategy against Obama. Conservatives also are testing their own get-out-the-vote efforts against the well-organized unions in Wisconsin.
Q: Is this recall election only about Walker?
The recall of the governor has overshadowed several other recalls also on the ballot. Democrats and unions are trying to oust three Republican state senators who voted for the Walker law, and fill a fourth seat left vacant when a Republican senator resigned. If they can win just one of the four state Senate races, Democrats will have a majority in the state Senate and could block the Walker agenda or help a new Democratic governor restore union collective bargaining.
Walker's lieutenant governor, Rebecca Kleefisch, also is on the recall ballot.
Q: Who is likely to win?
Wisconsin has been politically polarized for more than a year and almost all voters have decided how they feel about him. Polls show Walker with a slight lead in the single digits.
This means the outcome of the recall will come down to which side can turn out its vote. Democrats and their allies are most influential in the capital Madison and the largest city of Milwaukee. Walker is strongest in rural areas and the suburbs of Milwaukee.
The nonpartisan agency which runs Wisconsin elections forecasts a turnout of 60 to 65 percent of voting age adults. Political analysts generally agree that Democrats need to push the turnout toward the 69.2 percent level of the 2008 presidential election to overcome Walker's small poll advantage. Walker won the governor's race in 2010 with a turnout of only 49.7 percent. The lower the turnout, the better his chances.
Q: Who are the winners and losers in the election?
If Walker wins the big winners would be the governor himself, the Republican party, the Tea Party and other conservatives who supported him.
The big loser would be labor unions.
Walker's opponent Tom Barrett calls the governor the "Rock Star of the Right." A victory would vault Walker into the conversation for national office. Walker said on Monday on Fox television that he is not interested in being Republican presidential nominee Mitt Romney's vice presidential running mate. But he probably would be mentioned as a future president or vice president.
The labor union movement, which launched the recall in the first place, would have spent a year and millions of dollars without success. They might be playing defense around the country as other states tried to follow Wisconsin.
Walker challenger Barrett would also be a loser. He would return to being Milwaukee mayor but after his third unsuccessful run for governor, his career in statewide politics would probably be over.
Obama might also be considered a loser if Walker survives. There might be grumbling that Obama did not visit Wisconsin to campaign for Barrett. The Wisconsin outcome would be another bit of bad news for the president, who has suffered setbacks recently from poor economic conditions and faces important Supreme Court decisions later this month on his healthcare law and the landmark Arizona immigration law.
If Walker loses, the big winners would be the labor unions, the Democratic party and possibly Obama. Losers would be Walker, the Republican party and its supporters.
A defeated Walker would be a political martyr to conservatives and could hit the Republican speech circuit. But his political career would be seriously compromised.
Victorious labor unions would immediately demand that the new governor Barrett restore their collective bargaining powers.
Obama would be seen as the likely winner in Wisconsin in November, making it harder for Romney to defeat the president.
There would be much questioning in the Republican party whether Walker's confrontational approach backfired. The defeat of Walker would be a setback for the conservative get-out-the-vote efforts. Critics of Super PACs would point to the massive spending and say that Walker's loss shows that rich conservatives such as the Koch brothers cannot buy elections.