FIGHT ON THE RIGHT.

Most days begin for Arlen Specter, the senior senator from Pennsylvania, with a game of squash around dawn, and they taper off in the evening after a couple of Martinis. "Martinis I find to be very relaxing," Specter told me recently, on an early morning of weak, gray light, with sleet blowing across the parking lot where we stood--in front of a medical office that abutted a mall alongside an interstate on the outskirts of Reading. Specter had just spent an hour urging a group of about a dozen doctors to vote for him in the state's Republican primary, on April 27th. Now he stood clutching a cell phone in one hand, holding his coat shut with the other, waiting for his Town Car to glide over and take him to a TV studio for an interview with a Christian broadcaster in Lancaster County. "I've been drinking Martinis since law school," he said, in the nasal drawl that serves as a constant, folksy reminder that, although he is a Philadelphia lawyer, he spent his boyhood in Bob Dole's home town, Russell, Kansas. "Martinis take a lot of the pressure off," he said. "Y'know, medicinally, there've been some recent studies that show they're good for you." Specter, who is seventy-four, has been a senator since he was fifty, and he's in the business of telling people what they'll be glad to hear. Gin as health food? Why not? The harder sell for him these days is himself.

Specter holds a prized seat on the Senate Appropriations Committee, and if reelected he is in line to ascend to the chairmanship of the Judiciary Committee--the sort of political real estate that should make winning renomination in a primary a cinch. But Pennsylvania's Republican primary is "closed" (only registered party members can vote), so the contest will be decided by an especially narrow slice of the general electorate: those who care most passionately about core Republican issues. For Specter, that means having to write off as much as a third of the primary vote in advance, on account of his steadfast pro-choice stand on abortion rights. Specter is an old-style centrist, one of the last of an aging and embattled breed of Republican moderates in a party that has moved steadily to the right in recent years. To some Republicans, like Paul Weyrich, a founder of the Heritage Foundation, who is regarded as one of the godfathers of the modern conservative movement, the thought of the Judiciary committee chairmanship going to Specter--a man who helped block Robert Bork's nomination to the Supreme Court--is a horror to be vigorously resisted. (In 1992, after Specter smoothed Clarence Thomas's path to the Court, Weyrich campaigned for Specter by telling voters, "Arlen Specter is an S.O.B., but he's our S.O.B.") So, while the White House and Senate leaders have endorsed Specter, his challenger, a third-term congressman from the Lehigh Valley named Patrick Toomey, comes armed with the blessings and the cash of Republican grassroots activists and heavyweights--including Bork, Weyrich, Edwin Meese, and Steve Forbes--who don't mind bucking the Bush machine in the hope of hardening the party line.

Pat Toomey is a conservative Republican of rigorous doctrinal purity: anti-abortion, anti-taxes, anti-spending (except for defense); a fiscal hawk, appalled by big deficits, a crusader for school choice, tort reform, Social Security privatization, and a smaller federal government. Before going to Washington, he was an owner of bars and restaurants in Allentown and, before that, an investment banker in New York, Tokyo, and Hong Kong. He is forty-two, a Catholic, the son of working-class Democrats and also a Harvard man, blond, meticulously groomed, with unnervingly white teeth and scrubbed pink skin. He has a tightly wound but forthright manner. "I was always very interested in public policy--a pretty wonkish guy, reading Social Security-reform proposals and things like that in my spare time," he said when I spent some time campaigning with him in central Pennsylvania. If Toomey has a sense of humor, he is careful not to flaunt it.

Toomey's voting record in Congress has won him nearly perfect scores on the ideological litmus tests of the American Conservative Union, the National Taxpayers Union, and Citizens Against Government Waste. The latter organization issues an annual "Pig Book," listing Congress's profligate pork-barrel spenders, whose sins have multiplied madly in recent years, in large part because President Bush has never used his veto power. Arlen Specter was named "porker of the year" for 2003 in honor of his habit of signing off on appropriations bills packed with seemingly gratuitous, and often comical-sounding, federal handouts.

"The ridiculousness of these projects!" Toomey ...