In democratic countries, the true mark of a politician's triumph is not whether he transforms his own political party. It's whether he forces the opposition to renovate itself and become tweedledum to mimic his own success as tweedledee.

Thus did British Prime Minister Tony Blair this week earn his place in the Politicians' Hall of Fame. In electing the flashy, moderate, bike-riding 39-year-old David Cameron as its leader, the opposition Conservative Party decided it would draw its slogan in the next election from the venerable rock band The Who: "Meet the new boss. Same as the old boss."

Cameron himself underscored his deep desire to be like Tony in his first boffo appearance in the House of Commons on Wednesday. Cameron declared of Blair: "He was the future once." The line brought down the house, and it made Cameron's essential point: If Blair won because he was fresh and non-ideological, it was time for British voters to toss out the old model and bring in the new. But they were merely being asked to buy a cooler, updated version of the same product.

The Tories pray that Cameron will end their long horror show. It began when Blair was first elected in 1997, ending 18 years of Conservative rule, most of it under Margaret Thatcher. The Iron Lady disdained tweedledum politics and joined Ronald Reagan in a political revolution on behalf of a radical version of free-market ideology. Thatcher was so committed to individualism that she was once moved to say: "There is no such thing as society."

The Conservatives dumped Thatcher in 1990, after 11 years in power, for the amiable and less ideological John Major. He hung on for one more election before being routed by Blair. Since then, being a Tory has meant living through one identity crisis after another. Conservatives couldn't decide if they were losing because they had abandoned the hard, pure Thatcherite faith or because they had held on to it with too much fervor. On some days the Conservatives tried social tolerance, on others immigrant-bashing. It's been a mess.

Yet Blair himself paid tribute to Thatcherism. (She gets into that Hall of Fame, too.) He junked his Labor Party's old faith in "the common ownership of the means of production, distribution and exchange," once enshrined in the party's constitution as Clause Four. He replaced it with a mushier commitment "to create for each of us the means to realize our true potential and for all of us a community in which power, wealth and opportunity are in the hands of the many, not the few." Blair talked not about "the Labor Party" but about "New Labor," a brand as different from the old as Aston Martin or Jaguar is from Vauxhall or Ford.

But he differed from Thatcher in thinking there is such a thing as society ("community" is a quintessentially Blairite word) and in favoring strong, albeit modernized, social services. Blair's new balance -- less social than the old socialism, more social than Thatcherism -- has proved impossible to beat. And so the youthful, upper-class Cameron and his followers, known in the British press (I'm not making this up) as "Cameroonians," decided to beat them by joining them. In accepting his victory, Cameron promised "social action to ensure social justice, and a stronger society." Society exists after all.

You could almost see the "New Conservative" posters rolling out of the Tory print shop. "We will change the way we look," Cameron declared, promising to give women a much larger role in the party. "We need to change the way we feel. No more grumbling about modern Britain. I love this country as it is, not as it was, and I believe our best days lie ahead. We need to change the way we think." A new look, a new feeling, new thinking, a new world. Oh, and did I tell you? Cameron wants, above all, to be new. Blair has not yet sued for plagiarism.

By the time the next election rolls around in four years or so, Cameron will be running not against Blair but, most likely, against Labor's brilliant, slightly dour chancellor of the exchequer, Gordon Brown. A British friend has a sneaking feeling that Blair and Cameron may so overwork the concept that when the election finally comes, "new" will look very old indeed, and Brown could win as the newest old thing on offer.

The Who, by the way, had another great song, titled "Who Are You?" When the British Conservatives couldn't find their own answer to that question, they decided to be Blairites -- not original, perhaps, but better than grumbling, or losing.