Editor's note: Julian E. Zelizer is a professor of history and public affairs at Princeton University. He is the author of "Jimmy Carter," published by Times Books, and editor of a book assessing former President George W. Bush's administration, published by Princeton University Press.
Princeton, New Jersey (CNN) -- The success of Gov. Scott Walker and his fellow Wisconsin Republicans at stripping most collective bargaining rights from public unions has triggered a fierce political backlash.
Organized labor and its supporters have mobilized. They are prepared to fight the outcome in Wisconsin and, more broadly, to campaign across the nation against other state and national officials who seek to extend this assault on unions.
Commentators have noted that Republicans have unintentionally stimulated the kind of political energy within union ranks that has been lacking for years. They have also revealed that there is more public support for collective bargaining than many thought existed. Unions, many of whom have been disenchanted with President Obama's policies, are now more aware of the stakes of the 2012 election.
As the labor historian Nelson Lichtenstein recently wrote on CNN.com, "Unions are essential to represent workers at the bottom of this heap and make the whole system work in more equitable fashion. The drama unfolding in the state of Wisconsin is educating Americans to this reality."
Still, there is a big question looming about what the Democrats will do. While the position of Republicans is predictably anti-union, the reality is that for many decades the Democratic Party has maintained only a lukewarm relationship, at best, with organized labor.
The party leaders have embraced many of the arguments of their conservative opponents, characterizing organized labor as just another special interest group. The focus of Democratic officials on suburban middle class voters has caused them to drift away from some of the bread-and-butter issues that once animated their party.
During the presidencies of Franklin Roosevelt, Harry Truman and John F. Kennedy, and Lyndon Johnson, unions remained central to the Democratic coalition.
Much of the New Deal -- contrary to what some conservative pundits have been saying in recent days -- centered on ensuring the rights of workers to organize, providing a certain floor of protection to those who spent their lives on the shop floor, and increasing the purchasing power of working class Americans through higher wages.
The Wagner Act (1935) was a centerpiece of New Deal policy. It created the National Labor Relations Board and ensured the right of workers to join unions.
In addition to an ideological commitment to the rights of labor, Democrats depended heavily on the grass roots operations of unions during election time and their campaign contributions.
The relationship started to weaken in the 1960s. Many younger liberals were not as sympathetic to working class Americans, and were more interested in civil rights and anti-war issues. Business exerted enormous financial and political pressure against legislation that benefited unions with an intensity unmatched on other issues.
While Lyndon Johnson depended on organized labor to round up support for key bills such as the Civil Rights Act of 1964 and Medicare, issues of specific concern to unions found less support. Following Johnson, Democratic leaders have continued with a bias against a strong pro-union agenda. George McGovern's campaign in 1972 targeted suburban voters, African-Americans, middle class women and America's youth rather than the traditional base of support: unions and urban machine politicians. Party reforms had created a nomination process that severely weakened the traditional power brokers within the party.
The relationship between unions and Democrats almost totally broke down under President Jimmy Carter. Although Carter had depended on labor for his victory against President Gerald Ford in 1976, the president didn't give their issues much attention once he was in the White House.
He perceived labor as another interest group in Washington that had undermined the public interest and used public policy for its own objectives. When Carter only endorsed a modest rise in the minimum wage in 1977, AFL-CIO president George Meany called his position "shameful" and a "bitter disappointment to everyone who looked to this administration for economic justice for the poor." Labor's resentment was a central force behind Sen. Ted Kennedy's challenge in the Democratic primaries in 1980.
President Clinton infuriated labor leaders with his support of NAFTA and embrace of deregulation and limited government. "I think the workers will be so damn angry over NAFTA," said Michigan union leader Frank Garrison, "that you'll have a hard time convincing them to support him on anything else."
Initially unions were optimistic about President Obama. "You cannot have a strong middle class without a strong labor movement," the president said in March 2009. The president followed through with a series of executive orders and high level appointments that were sought by organized labor.
But soon the record turned out to be more mixed. Obama refused to give priority to the Employee Free Choice Act -- a measure pushed by unions that would allow them to organize workplaces through signatures rather than an election with a secret ballot -- and resisted labor's push for a public option in health care.
He has shifted his emphasis toward deficit reduction at a time many labor leaders think that reducing unemployment should be the top concern. Although Obama has depended on labor to build support for his program, he has not offered much in exchange for their help.
The Wisconsin battle will shine a spotlight on the Democrats to see where they stand on this issue. For many decades, party leaders have decided that making unions a priority was not the way to go. But organized labor remains central to the Democratic coalition, even as their numbers have thinned. In election after election, and campaign after campaign, unions have remained loyal friends to the party of FDR.
This battle will force them to decide whether they want to change course. The truth is that unions don't have anywhere else to go. Most would not turn to a Republican Party that has been far more hostile to them, challenging their right to even exist. But Democrats can't afford for unions and their members to have dampened enthusiasm for their party. Time and time again, the Democrats have seen that when they are in a tough battle, unions have been one of the most reliable parts of their coalition.
The opinions expressed in this commentary are solely those of Julian E. Zelizer.