Who could have imagined, say ten years ago, that gay rights would one day be an issue that progressives could embrace to their political advantage, dividing the conservative world?

For decades, of course, hot button social issues were used in the exact opposite way: to divide the Democratic coalition, driving a wedge between social liberals and more traditional working class voters. One of the main projects of an entire generation of DLC-type Democrats, most notably Bill Clinton, was to defuse these issues by backing away from strong liberal stances on many issues.

Now it's exactly such strong stances that end up dividing conservatives, with LGBT rights as a prime example. Just look at what's happening in Washington, with the employment discrimination bill that passed the Senate today.

The bill picked up just enough Republican votes to pass and now goes to the House. It's an important measure that extends crucial workplace protections to LGBT workers, and that's the main reason to cheer. But bringing the bill to a vote was also brilliant politics, since its passage now puts House Republicans in a very difficult—and increasingly familiar—situation: They can either side with their far-right members to block the bill, thereby further underscoring the GOP's reputation for intolerance—which alientates young, female, educated and nonwhite voters—or they can anger major elements of the conservative base, evangelical Christians and older Tea Party activists.

Playing to that base on social issues used to be compatible with winning elections. Indeed, divisive appeals on these issues helped mobilize the conservative base and affect electoral outcomes as recently as 2004, when gay marriage ballot initiatives were used to draw more evangelicals to the polls in swing states like Ohio. That game plan is no longer effective as Americans overall have embraced more progressive cultural values—a trend related to generational change and the fact that the nation's population has become better educated and more cosmopolitan in the past two decades.

Professionals make up a bigger share of the electorate in key places, as Ruy Teixeira has long pointed out, and bashing gays, immigrants, women, minorities and whoever else is a big turnoff to many of these voters. (Although by no means all voters, particularly when it comes to race, as Ian Haney López points out in his important new book Dog Whistle Politics: How Coded Racial Appeals Have Reinvented Racism and Wrecked the Middle Class.)

Who knows what will happen next. The interesting thing here is the reversal of political fortunes, with the right now fighting for unity on social issues (and economic ones, too) as moderates and ideologues pull the party in different directions.

No sooner will the fight over the discrimination bill subside than immigration reform will move back front and center—another worthy cause, but also another wedge issue that Democrats are exploiting to separate the crazies from the rest of the party.

None of this is to say that major divisions don't still lie within the Democratic coalition. For the time being, though, the wedge issue shoe is definitely on the other foot.