What if the public polls predicing a sizable labor win in the Ohio battle over collective bargaining are just flat-out wrong?

With many pundits predicting a comfortable win for unions, even pols like Mitt Romney seem to be edging away from the anti-labor side. But labor sources say predictions of victory in this fight — which has attracted intense national attention from both sides as a referendum on labor’s strength in the industrial heartland — are way premature.

An internal memo from a key labor-backed group in the state is flatly warning that the polls are “flawed” and that a big win for labor is not even “remotely possible.” It adds that the right’s messaging has “worked,” and that there’s good reason to suspect that a “massive amount of voter confusion remains,” suggesting the fight could still go either way.

“Those predicting a blowout for our side are basing their analysis on flawed public polling samples,” reads the memo, which was circulated to labor and political operatives involved in the fight by Brian Rothenberg, the executive director of Progress Ohio, which is partly bankrolled by labor. It was forwarded my way by a source.

“Modeling turnout for an off year ballot initiative is notoriously difficult,” the memo continues. “This is especially true in a state like Ohio where polling on ballot initiatives has been very unreliable.”

The memo singles out a recent Quinnipiac poll — which received much national media attention — finding that the pro-labor forces are ahead by 25 points. The poll found that opposition to SB-5, the centerpiece of GOP governor John Kasich’s legislative program, has almost doubled in the last month, with repeal now enjoying a 57-32 edge. (Poll numbers corrected.) The memo also singles out a Public Policy Polling survey that found similar results.

But the memo warns that the question wording in the two polls is so flawed as to be unreliable, because neither poll used the language voters will see on the Issue 2 ballot. “Keep in mind, neither of these polls tested the actual ballot language,” the memo says. “It’s a safe bet, if the actual ‘Issue 2’ language were polled that the margin would have been substantially narrower.”

The memo also points out that public polls on three previous Ohio ballot initiatives — a 2004 same sex marriage ban; a 2005 election reform initiative; and a 2009 measure to build casinos — were all off by wide margins.

“Bottom line: It’s nearly impossible to develop a reliable likely voter model for ballot initiatives,” the memo says, adding: “there are simply too many unknowns to believe these numbers are credible or even remotely possible.”

While such memos are sometimes leaked to the press to game expectations and goose turnout, this one bills itself as “our most candid assessment of where the `Issue 2’ measure currently stands.”

In a sense, the last minute warning is testament to how enormously high the stakes are for labor in this fight. National conservatives see this effort as absolutely critical to their efforts to break labor’s back in a key industrial swing state in advance of 2012, and right wing groups are pouring money into the state. For labor, which is also spending big money, a victory would be particularly sweet: It would challenge the conventional narrative that the failure to take back the state senate in Wisconsin signaled that labor’s influence is headed for irreversible decline.