One of the arguments Sen. Ted Cruz has made for defunding Obamacare is that even Big Labor, normally the Democrats' ally, is now against President Obama's health care bill. It's proof, he says, of Obamacare's extreme unpopularity.

Here's how the Texas Republican put it in a column Monday for "Even labor unions that once championed this law are decrying how it could destroy the 40-hour workweek for millions of middle-class Americans."

This is true as far as it goes. As I have repeatedly reported for the Washington Examiner, labor union leaders have expressed grave concerns over the impact of the Affordable Care Act.

But Cruz's statement leaves out an important bit of context: As unhappy as they may be, what those union leaders want is not a repeal of Obamacare, but an expansion of it that cuts them a special deal.

Big Labor's predicament regarding Obamacare is this: Most union leaders strongly backed Obamacare when it passed. They reportedly did so with the behind-the-scenes assurances that President Obama would fix certain elements they didn't like.

The two main ones are the law's tax so-called "Cadillac tax" on high premium health insurance -- which would apply to many union-negotiated plans -- and that the multi-employer insurance plans unions favor, also known as "Taft-Hartley" plans, are not eligible for federal subsidies.

Union leaders previously got a favor from Obama when the Cadillac tax was delayed until 2018. They haven't gotten the subsidies yet, though. That has many in Big Labor worried. They fear that without subsidies, employers will limit coverage, limit worker hours or simply pull out altogether.

At its national convention in Los Angeles, the AFL-CIO passed a resolution on Sept.11, urging action. It said the law "should be administered in a manner that preserves the high-quality health coverage multi-employer plans have provided ... if this is not possible, we will demand the ACA be amended by Congress."

"Amended," not repealed. This language was preceded by a long preamble which said the AFL-CIO agreed with the law's goals and was working with the administration to create a "legally supportable regulatory approach." In other words, to reinterpret the law so Taft-Hartley plans do get subsidies.

The resolution was, in short, a public message to the White House to get going on this. There are tell-tale signs that Labor Secretary Tom Perez is working behind the scenes to do just that.

It is true that some union leaders have talked repeal and a few have even endorsed it. But they remain a distinct minority within the larger labor movement.

If push comes to shove and the government is shutdown, expect to Big Labor to be squarely in the Democrats' corner.