A shrinking base, a high-profile defection skillfully managed by the other side, an idiotic delight at how the party is becoming “purer” — that’s the GOP today. And to British ears, it all sounds very familiar. It is distinctly reminiscent of the Conservative Party in Britain during the Tony Blair years.

As was the case with the Tories, many of the Republican Party’s big beasts can’t see the point in taking up its cause until the party is prepared to change. Tom Ridge, probably the only Republican who could win Arlen Specter’s Senate seat in Pennsylvania, has declined to run for it, saying last week that the party is “too doggone shrill” and needs to be “less judgmental.”

Ridge is right. The GOP is fumbling for direction. For one thing, it’s bickering over sex. While party central remains steadfast in opposition to same-sex marriage, some Republican state legislators in Maine and New Hampshire voted for it last week. But here’s a hopeful sign for the Republicans: In recent years, British Conservatives have managed to make social conservatism socially acceptable again.

They’ve done it through three key moves: enthusiastically signing on to Britain’s liberal settlement on homosexuality, recasting pro-family policies as part of an anti-poverty crusade, and tying support for the family into a broader recognition that people aren’t motivated by profit alone.

As a result, in the past few decades, social conservatism has not been the political force in Britain that it has been in the United States. Most British voters don’t know their MP’s position on abortion or gay rights, and no politicians have had to embark on Romneyesque shifts in their social positions before every campaign.

The Conservative Party last attempted to harness social conservatism — with disastrous consequences — in the 1990s. In 1993, Prime Minister John Major launched a “back to basics campaign,” declaring, “We should condemn a little more and understand a little less.” Having defeated the statist postwar consensus on economics, the party set out to do the same on social policy. Single mothers were singled out for harsh criticism. It became a Tory talking point that young women were getting pregnant just to cut in line for state-provided housing.

Britain’s tabloids saw this moralizing as an invitation to expose the love-children, adultery, and other hypocrisies of Conservative parliamentarians. (Remarkably, Major had launched the campaign even though he had had an affair with a fellow MP only a few years before; this didn’t become public, however, until long after he had left office.) All of this contributed to the party’s rout in the 1997 election. Middle-of-the-road voters saw the Conservatives as hypocrites. As the party’s chairman acknowledged in 2002, the Conservatives were perceived to be the “nasty party.”

Because of this history, the Conservative achievement in making social conservatism socially acceptable is all the more remarkable.

In his first party conference as Conservative leader in 2006, David Cameron declared: “There’s something special about marriage.” But to the evident displeasure of some in the audience, he went on to say, “And by the way, it means something whether you’re a man and a woman, a woman and a woman, or a man and another man.” By embracing civil unions, going out of his way to equate them to marriage, Cameron established his credentials for talking about social issues without being dragged into a discussion of gay rights.

The Conservatives then turned the tables on those opposed to state support for marriage. A think tank led by one of the party’s former leaders amassed huge amounts of statistical evidence showing that married couples were more likely than unmarried couples to stay together when they had children, and that low-income children did far better in life if they were raised in a stable two-parent family. New Labor’s mantra of “what matters is what works” was turned back on itself, because the data showed that marriage helps the poor.

Cameron’s stance on social issues is crucial to keeping the party united. Many on the right are unhappy with his refusal to be explicit about how much government spending will have to fall to get the deficit under control. Or his reluctance to take on Labor more aggressively over its plans to raise taxes on income above 150,000 pounds (roughly $228,000) to 50 percent. But the belief that Cameron will tackle the country’s social problems has kept them in line.

The polls show the Conservatives on course for a landslide victory in the next election, slated for the spring of 2010. It is tempting to say that Labor has managed the public finances so disastrously that the opposition will win no matter what. But Cameron doesn’t alienate voters the way previous Conservative leaders did. Despite the bitterly anti-politics mood in Britain — according to a poll by the British polling firm Populus, two-thirds of voters think that a majority of MPs don’t play by the rules and are improperly using government funds — 56 percent approve of Cameron, according to another recent poll, while only 31 percent disapprove.

If the Republicans had those kinds of numbers, the cynical opportunists would be joining the party, not leaving it.