On Saturday, August 11, some 40,000 union members descended on the City of Brotherly Love for what was billed as the first-ever “Workers Stand for America” rally. The ostensible purpose of the rally—organized by the International Brotherhood of Electrical Workers and AFL-CIO—was to gather support for a “Second Bill of Rights,” defined by IBEW president Ed Hill as “full employment and a living wage; full participation in the electoral process; a voice in the workplace; a high-quality education; a secure, healthy future.”

These familiar liberal shibboleths sound rather anodyne and toothless for a union rallying cry. Indeed, labor leaders at the rally were quick to clarify that these were broad policy sentiments, not specific demands. The Second Bill of Rights is a ginned-up excuse for the gathering’s real purpose: firing a shot across the bow of the Democratic party.

Unions are very unhappy that the Democratic party decided to hold its convention in Charlotte, North Carolina—a right-to-work state that forbids compulsory unionism. Indeed, organizers in Philadelphia not so -subtly included two news articles in the press kit. The first was a National Journal piece headlined “Unions Divert Democratic Convention Money to Rally for Worker Rights: The sour relations could cost convention fundraisers millions in lost contributions.” The other was a CBS News story: “Unions shifting money, resources away from Democratic convention.”

Which is not to say that relations between Democrats and their biggest supplier of campaign cash are openly hostile—at least not yet. The rally at Eakins Oval, about 200 yards from the famous “Rocky” steps, opened with a video montage that included Pat Gillespie of the Philadelphia Building and Construction Trades union condemning “teabaggers and Republican manipulators.”

Also speaking at the rally was Rep. Debbie Wasserman Schultz, head of the Democratic National Committee, who was happy to regurgitate the obligatory platitudes: “The Second Bill of Rights is so incredibly important so that we make sure that we can reinforce our focus on fighting for the middle class,” she told the crowd. But much of her speech was a predictable Mediscare jeremiad against her fellow House Budget Committee member, Rep. Paul Ryan, who had been announced that morning as Mitt Romney’s running mate.

Offstage, Wasserman Schultz’s support for the union agenda was less than full-throated. Mike Elk, a reporter for the left-wing In These Times, asked whether she supported the mayor of Charlotte’s position that public employees should have the right to opt out of paying union dues. “What I know is that Democrats are thrilled and excited about making sure that we put on the most open and accessible .  .  . political convention ever,” she said, dodging the question.

Aside from Wasserman Schultz, the other big-name speaker at the rally was AFL-CIO head Richard Trumka. Trumka is straining at the bit these days, having to constantly offer half-hearted defenses of the White House to his union brethren. One flashpoint between unions and Democrats is the Keystone XL pipeline, which would transport oil from Canada to refineries in Texas. The construction of the pipeline would provide lots of good union jobs and is also supported by Republicans. However, the Obama administration’s fealty to progressive environmental groups has thus far prevented the pipeline from being built, angering unions and upsetting relations with Canada.

Asked by The Weekly Standard about the Obama administration’s decision to hold up the pipeline, Trumka deflected the question. “Yeah, I think we can get it done in the second term,” he said, adding that building the pipeline and minimizing its environmental impact is not an “either-or” proposition.

The Keystone pipeline is just the latest example of how labor leaders’ lining up behind left-leaning politicians can put them at odds with the workers they supposedly represent. Union affiliation still tends to be tribal rather than political—many union members are socially conservative, and a nontrivial percentage vote Republican. You would never see the hundreds of American flags at an upscale progressive rally that you saw at Workers Stand for America.

When I asked Trumka whether union members’ support for Obama is waning because of the White House’s hostility to gun rights and the recent conflicts with the Catholic church, his nostrils started flaring so fast his trademark mustache was practically flapping in the wind.

“You know who Bryce Harper is? I’m tempted to say, ‘That’s a clown question, bro,’ but I won’t. In every election there’s a union difference. .  .  .  I can go down gun owners, veterans, the elderly—anything you want to call, there was a major union difference” in determining the outcome.

No one doubts that union support for Democrats makes a difference in elections. The question is, in 2012 will the union difference be enough? The 2008 election was the biggest all-out political effort by unions in decades. Organized labor spent $400 million, and the result, while convincing, was not a landslide. Union support for Obama wouldn’t have to go down much for Romney to win.

How’s this for an indicator? The week prior to Trumka’s trumpeting the “union difference,” the United Mine Workers of America—which Trumka himself used to head—announced it was declining to endorse Obama thanks to the administration’s job-killing EPA regulations. The same union had enthusiastically endorsed him in 2008.

For their part, there are signs that Democrats are worried about the level of union support in this election. The day before the Workers Stand for America rally, the DNC quietly announced in a Friday afternoon news dump that it was moving all its money and banking business to Amalgamated Bank, a labor-owned institution with a troubled history.

Last year, the bank was subject to an FDIC enforcement action, owing to varieties of accounting chicanery designed to make the bank’s balance sheet appear stronger than it was. The bank’s low liquidity levels were resolved in part when two private equity companies, W.L. Ross & Company and The Yucaipa Companies, each took a 20 percent stake in Amalgamated. (The Yucaipa Companies is chaired by billionaire Ron Burkle, whose close friendship with Bill Clinton has consumed much tabloid ink over the years.)

Still, there are many indications that such sops to unions may be too little, too late, and that the Obama campaign won’t be able to amp up union enthusiasm to the levels it needs. “If you doubt that Republicans and labor can find common ground, consider the record of a governor named Romney—not Mitt, but his father, George,” the IBEW’s Ed Hill wrote in a Philadelphia Inquirer op-ed published the same day as the rally. “As governor of Michigan during the 1960s, he signed that state’s Public Employee Relations Act, guaranteeing government workers the right to organize and bargain collectively.”

It seems unlikely that Mitt Romney will adopt his father’s positions on organized labor, but labor leaders appear braced for the possibility that, come January, they’ll have to work with him whether they like it or not.