Etiquette holds that you “dance with the one that brung you.— But politics is clearly not guided by Emily Post, and the public may be “cutting in— between Democrats and their top benefactor. A key strategic question for Democrats this fall is whether they jilt the public or organized labor.

Who “brung— the majority of Democrats into the 111th Congress is no mystery.

During the 2008 elections, organized labor pumped hundreds of millions of dollars into campaigns to help elect a Democrat to the White House and Democratic majorities in the Senate and House of Representatives. The spending didn’t stop on Election Day though; CQ Today reported that in the first six months of 2009, unions outspent all other special interests by dropping more than $10 million of their members’ money on lobbying.

The windfall dollars-for-influence relationship would be profitable for both parties as long as unions were seeking low-profile, low-cost parochial help.

However — notwithstanding a few inside baseball Department of Labor regulations and promises to take another look at that onerous government oversight of the squeaky-clean Teamsters — it’s not small-ticket items that union bosses have included on their federal wish list.

The problem for Democrats is that the policy returns that union officials want for their investment may come at a high political cost.

Last December, the powerful president of the American Federation of State, County and Municipal Employees confided of his political investment, “The payback would be Employee Free Choice Act.— Yet while that policy would be good for unions — which stand to reap billions in new dues dollars — the politics are lousy for most of the public. EFCA’s secret-ballot-killing provision truly is anti-democratic in both senses of the term.

After the business community ran tens of millions of dollars in ads against the anti-democratic measure, Sen. Tom Harkin (D-Iowa) acknowledged, “Certain words have gotten toxic, like card check,’ so we don’t use those words anymore.—

Poll after poll continues to demonstrate that the more voters know about EFCA, the less they like.

Perhaps even more toxic than card check may be the fight for a health insurance reform, dubbed by union officials as their top domestic policy priority. Gallup polling shows more Americans think their costs will increase than those who believe costs will go down. Moreover, the plurality of adults think the quality of care will decrease rather than increase if the government runs health care. AARP members have dropped their association by the tens of thousands. Throw in a low public opinion of Congress and a view that the august body isn’t able to handle a complex issue, and the result is another major political loser.

The health care reform problem is a special conundrum for the relatively but decreasingly popular President Barack Obama, with Gallup editors recently warning: “This leads to a circularity in which Obama’s hard push for health care reform may hurt his approval ratings, and his falling approval ratings may hurt his credibility on health care reform.—

Of course, EFCA and health care reform are both set against a back drop of a public angry at out-of-control spending and a surprisingly well-informed electorate unhappy about the House cap-and-trade legislation passed in June.

There’s a more fundamental problem, though. It’s not just the union-driven issue profile that’s working against Democrats; it’s being associated with recent unpopular union antics. Members of the Service Employees International Union have shown up at town hall meetings throughout the August recess to defend socialized care and offend protesters — even sparking allegations that union goons attacked a disabled black conservative in St. Louis.

That’s surely not the face Democratic leaders want. And indeed, it’s not even the face that unions want. AFL-CIO president-elect Richard Trumka has bristled that SEIU president Andy Stern “isn’t the face of organized labor.—

This comment comes from the guy who pleaded the Fifth during a federal investigation into a Teamsters money-laundering scandal.

The obvious answer for Democrats would be to tell organized labor to be patient and accept incremental change. But that seems unlikely to fall on favorable ears.

Stern and Trumka have seen labor left at the altar by previous administrations and have each issued their own warnings to Democrats on Capitol Hill. Stern’s union has set up a $10 million retribution fund to visit upon Democrats who don’t toe the line, while Trumka recently warned, “If you stab us in the back on Employee Free Choice Act and on health care … don’t you dare, don’t you dare ask for our support next year!—

That, of course, makes for an interesting showdown as most Members of Congress prepare to seek re-election in 2010.

Between Democratic leadership, the public and organized labor, two’s company and three’s a crowd. Someone is going to get dumped, and leading Democrats will have to choose whether it’s Big Labor or themselves.

Bret Jacobson, a founder of the consulting firm Maverick Strategies, which assists free-market think tanks and trade associations, has also been a senior research analyst for the nonprofit watchdog Center for Union Facts, which he helped launch in 2006.