For nearly an hour last week, the AFL-CIO’s 2013 convention in Los Angeles could have been mistaken for a Tea Party rally.

One union leader after another took to the floor to bemoan the impact that the Affordable Care Act – aka Obamacare – would have on their members’ health care plans and to demand that President Obama fix this.

Many unions provide health insurance to members through multi-employer plans. Under Obamacare, those plans’ costs will rise, causing many employers to limit coverage and raise premiums – or pull out altogether.

What went unremarked by the union leaders was that the AFL-CIO had backed Obamacare in the first place. It – and several of its largest member unions – were part of the liberal coalition group Health Care for America Now that pushed for the law.

When Obamacare passed in March 2010, AFL-CIO President Richard Trumka lauded it as a “momentous step forward.”

The American Federation of Teachers President Randi Weingarten said, “Congress and the White House have now given Americans what they need and deserve.”

United Food and Commercial Workers Union President Joe Hansen even called it “an achievement that will rank among the highest in our national experience.”

That was then. Three years later, that same law is creating “unstoppable incentives,” as Hansen put in a May op-ed, for companies to dump employees onto the law’s healthcare exchanges – eliminating one of the main benefits many unions provide to their members.

Why did the union leaders not see this coming? Reportedly they did, but were given behind-the-scenes assurances by Obama that these problems would be fixed.

The administration hasn't acted, though. That's perhaps because giving the unions the fix they want would cause Obamacare's costs – already steep and increasing – to soar $187 billion over a decade, according to one estimate.

"Since the ACA was enacted, we have been bringing our deep concerns to the administration," UFCW's Hansen and two other union leaders, the Teamsters' Jimmy Hoffa and Unite Here's D. Taylor, said in July letter to Democratic congressional leaders. "[O]ur persuasive arguments have been disregarded and met with a stone wall by the White House."

So in exchange for being good soldiers and helping to pass Obama’s key initiative, union leaders got major problems for their existing health care plans in return. That’s not much of deal.

That frustration boiled over at the LA convention. Many speakers recalled's Obama's promise to them at their 2009 convention that people could keep their existing health care coverage.

“We are seeing employer after employer cut hours so as to avoid the 30-hour definition of a full-time job. We are seeing this in our union,” said Loretta Johnson, AFT secretary-treasurer.

Several painted the problem in apocalyptic terms. Sheet Metal Workers International Association President Joe Nigro warned that if nothing is done, the membership losses would mean the AFL-CIO could hold their next convention in a building “one quarter” the size.

Laborers' International Union of North America President Terry O’Sullivan talked openly of repeal.

In the end, only the California Nurses Association did not back the federation’s resolution calling on the administration to either protect multi-employer plans or for Congress to amend the law – and that was because it wasn’t radical enough. (“A market-based approach has no place in healthcare,” CNA board member Kathryn Donahue said.)

Their pleas did not move the White House. In a meeting with labor leaders Friday, administration officials, including Labor Secretary Tom Perez, flatly turned down their request to extend tax credits to offset the higher costs created by Obamacare.

That’s tough luck for the union leaders – and even tougher luck for the people they purportedly represent. The rank and file might want to start asking their leaders some hard questions.