Milwaukee Mayor Tom Barrett has won the Democratic primary to face Gov. Scott Walker (R) in a recall election next month.

The recall will be a rematch. Barrett lost to Walker by five points in 2010. Since then, Walker has been under fire from unions for stripping public employees of their collective bargaining rights.

“Tonight, I am humbled by and grateful for the support of Wisconsinites across our great state,” Barrett said in a statement. “[W]e are united in knowing that we must work together to end Scott Walker’s ideological civil war.”

Barrett was not the preferred candidate of the public employee unions who sparked the recall. That was former Dane County Executive Kathleen Falk. But Barrett benefited from higher name recognition and political establishment support.

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Unions quickly rallies around the nominee. “Tom Barrett is a strong leader who will end the political turmoil Scott Walker has brought to this state and reunite Wisconsin to get us moving forward again,” said Kristen Crowell, executive director of the labor coalition We Are Wisconsin.

“AFSCME members have been proud to support our friend Kathleen Falk,” said AFSCME Council 24 Executive Director Marty Beil. AFSCME clashed with Barrett in Milwaukee and criticized him more harshly than other unions in the primary. “But the ultimate goal has always been to defeat Scott Walker.”

Falk herself encouraged her supports to help Barrett, saying in a statement that “the next four weeks may be the most important in our state’s history.”

The movement against Walker began with protests in February of 2011 and quickly turned into an extended recallcampaign against the Republicans who instituted the collective bargaining reforms.

Democrats attempted to take control of the state Senate last summer; they ousted two Republican legislators but fell one seat short of control. Last fall, nearly a million Wisconsinites signed petitions to recall Walker. He will be on the ballot on June 5 with Lt. Gov. Rebecca Kleefisch and four more Republican state senators.

Firefighters union president Mahlon Mitchell easily won the Democratic primary to take on Kleefisch.

Walker has far outraised and outspent his Democratic rival. Taking advantage of laws that allow a recall target to raise unlimited funds, he has brought in $25 million and spent $20 million. Barrett has raised less than a million dollars and will have to ramp up quickly to compete.

If Barrett wins it will be the third successful gubernatorial recall in history. It’s also Barrett’s third try at the governor’s mansion. Turnout for Walker in the perfunctory GOP primary was high, a sign of Republican enthusiasm.

“As Milwaukee Mayor Tom Barrett enters the general election in his soon to be third statewide losing campaign, he will surely find that his record of raising taxes and promises to continue to do so will not resonate with voters,” said Friends of Scott Walker deputy campaign manager Dan Blum.

Yet despite Walker’s massive investment, polls show the state evenly split between the two candidates. Few voters are undecided, so turnout will be the key to victory.

Collective bargaining has been overshadowed among voters by jobs and the economy. Wisconsin has had the worst job growth in the country, although unemployment is at its lowest since 2008. Walker is far from his goal of creating 250,000 new jobs.