* Recall vote for governor an early test of voter sentiment
* An early benchmark for the presidential race?
* If recall of Walker fails, Romney could get a boost
By John Whitesides
LA CROSSE, Wisconsin, June 2 (Reuters) - The battle over whether to recall Wisconsin's Republican governor, Scott Walker, has sharply divided the state and become a nationally watched test of his party's push to limit government, slash spending and challenge public-sector labor unions.
Tuesday's recall vote also has the attention of two very interested outsiders: Democratic President Barack Obama and Republican Mitt Romney, who are gearing up for their Nov. 6 showdown for the White House.
Whatever happens when Wisconsin voters decide whether Walker should be replaced by Democrat Tom Barrett, the repercussions promise to echo deep into the presidential campaign.
At a time when national polls show Obama and Romney in a virtual tie, both sides see the wrangling in Wisconsin as a chance to organize and gain early momentum in a politically divided state that could be crucial in determining who wins the presidency.
The recall battle has raged for months, sparked by Walker's elimination last year of most collective bargaining rights for public-sector unions. That led to huge street protests in Madison, the state capital, and to the recall effort that will culminate in Tuesday's vote.
Walker's national supporters see the recall as a referendum on his take-no-prisoners brand of fiscal conservatism, and both sides in the presidential race plan to scour Tuesday's results to gauge the mood of the electorate heading into November's bigger battles.
"The vote here will definitely be seen as a harbinger of things to come," said Wisconsin-based Republican consultant Mark Graul. "The winning side will have tremendous momentum, and there will be implications far beyond Wisconsin."
Wisconsin has not backed a Republican in a presidential election since it went for Ronald Reagan in 1984, but Republicans hope a recall win will demoralize Democrats and sharply boost Romney's hopes.
Most recent polls have shown Walker ahead of Barrett, who is the mayor of Milwaukee, by about 7 percentage points in the recall election. But in a reflection of how difficult it can be to read the political tea leaves in a "swing" state such as Wisconsin, polls have shown Obama ahead of Romney by 6 to 10 points.
Obama easily captured Wisconsin by 14 percentage points in the 2008 election, when he defeated Republican John McCain. Two years later, Republicans in Wisconsin roared back to elect Walker, defeat Democratic U.S. Senator Russ Feingold and take over the state legislature.
"If the governor is successful" in warding off a recall, "it will show the mood of voters is closer to where it was in 2010 than in 2008," Graul said. "And that could portend trouble for Obama here and in other similar states, like Ohio," another Midwestern state that will be perhaps the most significant battleground in the presidential race.
'ROCK STAR FOR THE RIGHT'
Walker's bulldozing approach to cutting state budgets has made him what Barrett derisively calls "a rock star for the far right."
Walker's rising status in the Republican Party has been evident as fellow Republican governors such as Bobby Jindal of Louisiana and Chris Christie of New Jersey have appeared with him in Wisconsin.
Former President Bill Clinton, a Democrat, campaigned in Milwaukee for Barrett on Friday, attacking Walker's "divide and conquer" approach to governing and warning that Walker's conservative allies will be emboldened if he wins.
The Wisconsin recall has offered another glimpse of how unfettered spending by partisan groups outside the campaigns can drive the conversation in elections - a poignant message as such groups have begun spending what they estimate will be hundreds of millions of dollars on the presidential race.
Conservative groups such as Americans for Prosperity, funded by the billionaire conservative brothers Charles and David Koch, have poured millions of dollars into Wisconsin and plastered the state's airwaves with anti-Barrett ads. It is part of an effort to make a statement for their conservative cause - and set a tone for the presidential election.
Walker has raised $31 million to Barrett's $4.2 million, and by late April about two-thirds of Walker's 2012 donations had come from out-of-state donors, according to finance reports compiled by the Wisconsin Democracy Campaign, which tracks money in state politics.
"If Governor Walker survives this, then national Republican and conservative leaders are going to see him as the spearhead for a movement," said Joe Heim, a political scientist at the University of Wisconsin-La Crosse.
Romney and Obama have avoided much involvement in the Wisconsin race, perhaps a sign that the presidential candidates are not willing to risk being tied too closely with either side.
When Romney was in Wisconsin to campaign in the state's April 3 presidential primary he called Walker a "hero." Obama endorsed Barrett in a brief statement after the May 8 Democratic primary but has said nothing publicly.
Even some Democrats think Barrett has run an ineffective, uninspiring campaign with his attack on the governor's leadership that moved beyond Walker's push for anti-union legislation.
Barrett has targeted Walker's record on creating jobs and raised questions about a criminal probe into whether Walker's aides when he was Milwaukee County executive did political fundraising on public time.
But after months of polarized battle over Walker's agenda, most Wisconsin voters seem to have made up their minds. A recent Marquette University law school poll said just 3 percent of voters remain undecided; a Democratic poll this week put the figure at 1 percent.
That makes voter turnout a potentially huge factor in the recall vote. Both sides have promised unprecedented get-out-the-vote operations.
"We've said all along this will be very close and will be decided by turnout, and we think we'll have the most effective turnout operation," Wisconsin Democratic Party Chairman Mike Tate said.
While Democrats have a slight edge in voter registration in Wisconsin, Republicans seem to have at least a slight edge in enthusiasm. The Marquette poll found 91 percent of Republicans were "absolutely certain" to vote, compared with 83 percent of both Democrats and independents.
'A DRY RUN'
"When I make calls, I get Republicans who are really angry this is happening. The Democrats are mad too, but I don't think they are as passionate about it," said Chris Johnson, a retired teacher who volunteers at a Walker field office in La Crosse.
Walker has opened 22 offices around the state to direct his turnout operations, and he said volunteers have made more than 2 million calls to voters - more than during his entire 2010 race.
Volunteers made more than 200,000 contacts with voters on a recent weekend day, and other Midwestern state Republican parties are setting up their own phone banks for Walker.
Volunteers with the state Democratic Party knocked on 100,000 doors that same weekend day, and labor groups also have set up their own networks of more than two dozen field offices.
The turnout operations will serve as a test run for November's presidential contest. Tate said there was significant overlap, for example, between the state Democrats' field staff and Obama's campaign.
Some Wisconsin Democrats have grumbled about the lack of support from the national party.
The Republican Governors Association was one of the biggest spenders in the race, pumping in nearly $8 million, while the Democratic National Committee only sent out a late fund-raising appeal last week.
State officials are predicting a big turnout on Tuesday, and Democrats are targeting people who voted in 2008 but not 2010. They are hoping to get 150,000 to 200,000 recall voters to the polls who did not cast a ballot in 2010 - when Walker won by about 100,000 votes.
The risk is that the losers will be demoralized after the intensity of the recall fight, making it harder to get them back to work in the campaigns for November's presidential election.
"It's very easy to burn out the average political volunteer. I'm not sure how easy it will be to get people back through the door in September," said Brian Westrate, the Republican chairman in Wisconsin's Eau Claire County. "But it will be a lot easier if we win."
(For full coverage of the U.S. presidential campaign please click on ) (Editing by David Lindsey and Vicki Allen)