YOU'VE GOT to hand it to Karl Rove, the White House political guru. The man is one shrewd operator.

Capping a campaign that was steeped in irony, he and his associates last week managed to essentially wrench the Republican primary away from Rhode Island Republicans -- or, at least the party's base -- and turn it over to thousands of Democrats and independents.

He did it in hopes of re-electing incumbent Lincoln Chafee. Though Mr. Chafee has actively opposed President Bush in the key areas of taxes, the courts, and the war on terrorism, Mr. Rove concluded that Mr. Chafee was the only Republican who stood a chance of winning in November in Rhode Island. And the GOP may need that seat to retain control of the Senate.

In essence, Mr. Rove betrayed Republicans here for the greater "good" of a GOP-run Senate.

It was a cunning, and stunning, act of realpolitik. I thought the odds were against him, but he pulled it off brilliantly.

The numbers made it look like it wasn't that close: Mr. Chafee beat Cranston Mayor Stephen Laffey, 54 to 46 percent.

But think about it: Mr. Laffey, who slaved day and night traversing the state, holding signs and greeting voters, ran a remarkable grassroots campaign.

Running against an incumbent with the golden Chafee name who had the support of the party's establishment, Mr. Laffey captured 29,500 votes, easily eclipsing the previous all-time vote-getting record in a Republican primary, Sen. John Chafee's 27,906 in 1994. The mayor got more votes than Donald Carcieri and James Bennett combined in the 2002 GOP gubernatorial primary.

By any measure, that was an astonishing achievement by a two-term mayor with no previous political experience. The party's conservative core was passionately with Stephen Laffey, and in big numbers.

But Mr. Rove and company flattened him, and them, with the force of a tsunami.

In what The Washington Post's Chris Callizza called "a dry run for the fall," the Washington GOP machine imported activists from around America to get hands-on experience.

They exploited a quirk in Rhode Island law, letting undeclared voters participate in any party's primary. Chafee supporters coaxed large numbers of Democrats to disaffiliate -- Warwick Mayor Scott Avedisian offered the figure of 1,600. And the Rove forces poured in millions of dollars to micro-target Chafee supporters with highly sophisticated polling and computer analysis. They ran a big get-out-the-vote campaign, and aired brutal ads attacking Mr. Laffey's character to try to suppress his support. Mr. Laffey, for his part, refused to run such scurrilous ads, something analysts called a costly error -- though the Club for Growth, a conservative group that heavily backed the mayor, ran ads denouncing Mr. Chafee's record.

On Election Day, I noticed a man in a dark suit, wearing a Chafee button, with a cell phone shoved in his ear -- apparently some kind of Washington operative -- carefully monitoring the goings-on at the sleepy polling place where I voted. They had this election covered. Meanwhile, poll workers reported an unusual number of people instantly disaffiliating after voting Republican, suggesting that a large number of independents and Democrats took part.

The result? The turnout was a staggering 65,000 voters -- shattering the previous record by tens of thousands. In its test run, Mr. Rove's machine hummed like the engine of a Lamborghini.

As Mr. Callizza noted: "The ability of national Republicans to identify and turn out like-minded voters should give those predicting a massive Democratic wave this fall at least some pause. Midterm elections are typically low turnout affairs, and the party best able to motivate its base . . . usually wins."

Mr. Rove proved that a GOP senator from the Ocean State may utterly ignore the wishes and values of mainstream Republicans, and still win his primary. That frees Mr. Chafee to be even less supportive of the administration from here on out.

But the key, to Mr. Rove, is winning the Senate -- not having Mr. Chafee's help on policy. In his view, any Republican from Democratic Rhode Island is a gift from the gods -- no matter how liberal he is, and no matter how much that demoralizes the state's conservative Republicans.

Senator Chafee, son of the late, greatly admired senator, certainly seems in a better position to win in November than Mr. Laffey would have been. In the general election, his bold independence, his liberal values, his anti-Bush rhetoric and his last name -- in Rhode Island, Chafee is a political brand almost up there with Kennedy -- come into play and help tremendously. If low-key and awkward, he strikes people as likeable.

His Democratic foe, the smart and ambitious Sheldon Whitehouse, will be helped by the utter dominance of Democrats in the state. But Mr. Whitehouse, son of an ambassador, is far from a dynamic campaigner. Some people find his personality grating, and he sometimes seems to think that he is owed power by Divine Right. (He once blurted out that he was "bred" for leadership.)

In other words, it should be close. One thing is clear: This Battle of the Blueblood Liberals is the matchup Karl Rove dearly wanted in Rhode Island.

Edward Achorn is The Journal's deputy editorial-pages editor. His e-mail address is eachorn@projo.com.