The Republican "wing-nuts" -- my friend Evan Thomas's affectionate term for hard-line right-wingers -- are peeling off. Sen. Bob Smith, one of the bevy of very conservative presidential pretenders, has just left the Republican Party. Proclaiming his candidacy "pro-life, pro-Second Amendment, pro-military, pro-sovereignty, pro-character and integrity" and denouncing Republican leaders, he declared he will run as a third-party candidate.

Fellow wing-nuts Gary Bauer and Pat Buchanan have praised Smith's show of "principle." Indeed, Buchanan is, as always, but one threat away from bolting the Republican Party and running solo too. Pitchfork Pat has recently met with Jesse Ventura, who, as the only Reform Party major officeholder, controls the purse strings to the $13 million federal campaign money the Reform Party inherits from Ross Perot's 1996 run.

Why is this happening? Because of the Republican stampede to George W. Bush. The wingers' bitterness at the Republican establishment's embrace of Bush is palpable. W., they say, is nice enough and attractive, but how does a novice of modest accomplishment and vague views become the instant front-runner and break the world indoor record for fund-raising?

Answer: The brand-name surname, of course. But it is something else too. Republican swooning for George W. -- the smoothest, most moderate, least wing-nutty candidate of the lot -- reflects a tendency that has controlled the presidential nominations of both parties for the last quarter-century. Call it the Iron Law of Regression to the Center.

The law, invariable and infallible, decrees this: The longer a party has been shut out of the White House, the more it demands a moderate, bland, centrist candidate to win it back.

Take the Democrats. In 1972 they had been out of power for four years. Not long enough. They went to their left, George McGovern, and got crushed. By 1976, they had been out of power for eight years. They were a lot hungrier. They swallowed their ideology and went for the center, Jimmy Carter -- moderate and bland. They won.

Take the Democrats again in the Reagan-Bush era. In that cycle, they nominated, in succession, Mondale, Dukakis and Clinton. See a pattern here? Mondale ('84) was the most liberal and orthodox. Dukakis ('88) was more moderate, famously claiming that his nomination was about "competence, not ideology." And Clinton ('92) was as far to the right as you could get and still be a Democrat. He was a self-styled "New Democrat," one of the founders of the centrist Democratic Leadership Council.

The Democrats chose Mondale when they had been only four years out of power. By the next election, then eight years out, they were ready to compromise ideologically. Hence Dukakis. By '92 and 12 years, the agony was too much. They would buy any ideology to win. They bought Clinton's. And they won.

Take the Republicans. In 1980, they were only four years out of power. In accordance with the Iron Law of Regression to the Center, they were not yet ready to regress to the center. They chose Reagan, the ideological candidate.

The twist on this one is that they won. Parties usually lose when their candidate is a winger. But 1980 was an unusual year, and Reagan was an unusual candidate. The country was reeling; Carter was discredited by inflation, gas lines and the hostages. And Reagan was a wing-nut with a smile. So he won.

Fast forward to the '90s. In 1996, only four years out of power, Republicans went with an orthodox conservative, Bob Dole. Not a wing-nut, to be sure, but a man with a reliably and demonstrably conservative record.

By 2000, however, they will have had eight years of Clinton, years of humiliating defeats over budgets, the downfall of two House speakers, and a jujitsu loss on impeachment. They are desperate to win. Hence the mania for the safe, soothing, center-leaning George W. Never in a generation have the Republicans been more willing to give the benefit of the doubt to a candidate whose ideology remains obscure. Eight is enough. They want the White House.

Note that in 1996, still only four years out of power, Republican voters could flirt seriously with the ideological candidacy of Pat Buchanan, even giving him victory in New Hampshire. It is hard to imagine Buchanan carrying New Hampshire -- or anything -- in 2000. The party is just too hungry.

Buchanan and Smith and the others know this. Unless something cataclysmic happens to the economy or to the Republican Party, the wingers don't have a chance. (Which is why Smith has defected and Buchanan is feinting.) Anything for a winner. In America, you win (generally) by hugging the 50-yard line. And there bestriding it like a colossus is George W.