While the media focused on Wisconsin's 3 April presidential primary election, Wisconsin voters tuned in to another election: the 5 June recall election facing Wisconsin's conservative Republican governor, Scott Walker – the fallout from his 2011 anti-union legislative assault.

To recap: riding the November 2010 Tea Party political tsunami, Walker won on promises to reduce state budgets and taxes. Once elected, he claimed those priorities required dismantling public service labor unions, something he had neglected to mention in his campaign. With compliant Republican majorities in both legislative houses, he immediately proposed laws that functionally eliminated public-sector unions – depriving them of collective bargaining rights. Among other restrictions, government employers could no longer collect union dues, and unions had to win annual recertification elections.

Walker's initiative was part of a state-by-state Republican attack on public unions, institutional bases of Democratic support. Republicans gained nine 2010 governorships and 25 state legislatures. The campaign extended to Great Lakes states, traditional union strongholds. Indiana became an "open shop" state, restricting unions from enrolling all workers in represented workplaces. Ohio's Republican Governor John Kasich and the state legislature passed laws similar to Walker's.

Wisconsin electorates swing back and forth between Democrats and Republicans, with very liberal and equally conservative tendencies. But Wisconsinites also pride themselves on a common political culture of electoral fair play, open process in government, and labor harmony. The state was the first in the US to authorize the public-sector labor unions Walker is bent on eliminating. In light of the opposition he provoked, Walker now admits he may have overreached, acknowledging that he should at least have better prepared the public for his surprise union-busting attack.

Labor unions, Democrats, and an impressively broad progressive coalition of environmentalists, farmers, women, unions, minorities, and the elderly protested in unprecedented duration and scale. In defiance of 100,000-strong rallies, months-long vigils, and 14 state senate Democrats fleeing to Illinois to block a vote on Walker's proposals, Republicans passed Walker's bill in February 2011.

The protest coalition United Wisconsin responded with recall elections, and successfully unseated two Republican state senators in August 2011, reducing the 19-14 Republican majority to a one-vote 17-16 edge. United prepared for four more 2012 Republican state senate recalls – and the biggest prize of all: removing Walker himself.

Neighboring Ohio offered hopeful inspiration. In November 2011, Democrats and unions overturned Ohio's anti-union laws in a legislative referendum, by an overwhelming 61% public vote.

Recalling Walker required United Wisconsin to collect 540,208 signatures – one fourth of the votes cast in the previous gubernatorial election. From November 2011 to late January 2012, thousands of volunteers collected more than a million. To postpone elections, Walker and Republicans insisted that every signature be individually validated and electronically displayed online, a process that took more than two months.

On Thursday 27 March, the board responsible for state elections finished its painstaking assignment, reporting over 900,000 unduplicated, validated signatures. The next day, the board scheduled recall primary elections 8 May, and the recall general election 5 June.

With 900,939 validated recall petition signatures for an election that Walker won with 1,128,15 votes, momentum would appear to favor recall activists. Walker, however, has used the petition validation delay to raise a formidable campaign fund. A Wisconsin campaign finance loophole exempts incumbents facing recall from individual donation limits, from the time of submission of recall petitions until elections are scheduled. During that period, Walker flew around the country, including stops in New York City and Palm Beach, Florida, collecting donations of up to $500,000 per donor. From 11 December through 17 January alone, he reported $4.5m.

Political action groups have already aired television commercials attacking likely Democratic challengers. Independent analysts project recall election costs totaling $60-80m.

United Wisconsin also faces organizational challenges. Four Democrats will compete in the 8 May primary to challenge Walker, including Milwaukee Mayor Tom Barrett, who lost narrowly to Walker in 2010. Major Wisconsin public service unions support former Dane County Executive Kathleen Falk. The abruptly shortened election cycle, with less than a month between the primary and general recall elections, will challenge the Democratic nominee to match Walker's for name recognition, let alone compete with his ready funds and media blitz.

Democrats and United Wisconsin, though, insist that their thousands of volunteers and million petition-signers can offset Walker's financial advantage. Nor is this just any election. The issues and arguments have been aired so long and so loud that traditional campaign messages, advertising and soundbites may influence less than usual.

Whatever June's results, United Wisconsin has already won two significant victories. State and federal court decisions have overturned Walker's ban on workplace dues collection and annual recertification elections, breathing new life into public-service unions recently legislated for extinction. And the recall elections have already created a significant opening for the pivotal 17th, majority vote in the state senate: one challenged state senator, Wausau Republican Pam Galloway, unexpectedly resigned on 16 March, giving Democrats a 16-16 tie in the senate. If Democrats win even one of four contested recall state senate elections, they will recapture a majority, frustrating further legislative initiatives from Governor Walker and Republican representatives.

Only two state governors have ever been recalled in the United States: California's Gray Davis in 2003 and North Dakota's Lynn Frazier in 1921. A successful Wisconsin Walker recall, following Ohio's public referendum repudiation of that state's anti-union legislation, could become a significant rallying point for re-energized progressives come the 2012 November elections. The campaign has already reconstituted the once-demoralized Democratic coalition. Waking to the accelerating disparities of American income, wealth and political power, Wisconsin may offer a sign of things to come.