US Republicans claimed a "momentous victory" after Wisconsin's union-busting Republican governor survived a recall election aimed at ousting him mid-term.

Governor Scott Walker prompted mass protests -- and ultimately, Tuesday's rare special election -- after pushing through legislation last year to radically curb the power of public sector unions.

Late Tuesday, CNN, Fox News and CBS News all projected that Walker would keep his job with about the same margin as his initial 2010 election.

Republicans, who had cast the recall election as a referendum on their policies and a preview of the matchup between President Barack Obama and rival Mitt Romney, predicted a similar party victory in November's presidential election.

Romney said the results of the race -- which saw the Republicans outspend Democrats nearly seven to one -- would "echo beyond the borders of Wisconsin."

"Governor Walker has demonstrated over the past year what sound fiscal policies can do to turn an economy around, and I believe that in November voters across the country will demonstrate that they want the same in Washington, DC," Romney said in a statement.

"Tonight voters said 'no' to the tired, liberal ideas of yesterday, and 'yes' to fiscal responsibility and a new direction."

Wisconsin was one of a number of key battleground states that swept Obama to victory in 2008 and then handed control of the state legislature to Republicans in the 2010 mid-term elections.

"After tonight's results, Democrats and the Obama campaign are surely nervous," Republican National Committee chairman Reince Priebus said in a statement hailing Walker's "momentous victory."

"Wisconsin Democrats now head into November dispirited and in disarray, while Republicans remain strong and organized, with momentum on our side."

The Obama campaign shot back with a statement noting that the president won a nine-point advantage in exit polls, which showed "a very steep pathway for Mitt Romney to recover in the state."

Walker won 53 percent of the vote compared to Democratic challenger Tom Barrett's 46 percent, with 99 percent of the vote counted, CNN reported, citing unofficial results. An independent candidate took one percent.

Just two other governors have faced recall votes in US history, and both were ousted by angry voters.

"Tonight, we tell Wisconsin, we tell our country and we tell people all across the globe that voters really do want leaders who stand up and make the tough decisions," Walker said in a victory speech.

Obama had largely stayed out of the bitter battle, as polls pointed toward a likely victory for Walker.

While former president Bill Clinton visited Milwaukee last week to rally support for Barrett, Obama's endorsement took the form of a personally signed -- and rather late -- tweet on Monday.

"The Walker victory will embolden other Republicans elected in 2010 and give the Romney campaign more reason to focus on Wisconsin in the fall," said Barry Burden, political science professor at the University of Wisconsin - Madison.

While the Democrats will surely face criticism for failing to push harder to oust Walker, experts say the results remain a largely local phenomenon.

"I wouldn't say that this victory portends much for either party in November," said Kathleen Dolan, a political science professor at the University of Wisconsin - Milwaukee.

"An incumbent with an enormous spending advantage, much of it raised out of state, won the election."

Romney is not expected to have the same financial advantage over Obama, and the presidential election will be fought over different issues -- primarily the state of the US economy.

"It's a big victory for the GOP and Walker, but a big part of it is that people were sick of the recall turmoil that has kept Wisconsin off-balance for a year and a half," added Larry Sabato, director of the University of Virginia's Center for Politics.

"The November election is five months away, and a very different race."