The prospect of ever-higher taxes has Democrats distancing themselves from labor. New York Democratic gubernatorial candidate Andrew Cuomo is preaching fiscal prudence and says public pensions are “out of line with economic reality.” In California, old allies of labor like Los Angeles Mayor Antonio Villaraigosa (who was once a teachers union official) are also inveighing against the cost imposed by public unions. Oregon’s Democratic Gov. Ted Kulongoski, an attorney who once represented unions, is advocating clamping down on public-sector pay and benefits to fix that state’s budget problems.

Unions are also on the defensive in the culture wars. Later this month the documentary “Waiting for Superman,” about the failings of our public schools, will debut in theaters nationwide. The film is directed by Davis Guggenheim, who earned impeccable liberal credentials as the director of the Oscar-winning “An Inconvenient Truth.” His new documentary, say reviewers who’ve seen it, places a chunk of the blame for the woes of our schools on teachers unions and in particular paints Randi Weingarten, the head of the American Federation of Teachers, as an opponent of meaningful reform…

Of course even with its influence waning, labor can be a powerful electoral force. The AFL-CIO, SEIU and the American Federation of State, County and Municipal Employees have announced plans to spend about $100 million on the November elections. While that’s less than 2008, when unions gave $73 million in direct contributions to candidates and spent another $80 million independently on campaigns, the money represents a formidable commitment that could be a factor in close races.

Still, what we are seeing this year may mark a historic shift in American politics. If candidates around the country can repeat Mr. Christie’s strategy of winning office by taking on public unions, we could be witnessing a change akin to what happened in the late 1970s, when tax revolts in a handful of states created a nationwide momentum that eventually elected Ronald Reagan.