Arnold Schwarzenegger has come out of the Republican Party closet. He is, dare one say it, a moderate. He supports gun control and abortion rights and occasionally has a good word to say for government. His moderation has infuriated California Republican stalwarts who cannot decide if the pleasure of regaining the governorship is worth the pain of condoning Schwarzenegger's heresies.

Schwarzenegger cloaks his moderation on policy matters in radical political rhetoric. He talks like a populist. He points to the "enormous disconnect between the people of California and the politicians of California." He pledges to take California government away from the special interests and their political lackeys and return it to the people. On his Web site he promises to return California to the radical progressive principles of early 20th century governor Hiram Johnson. No mention is made of the conservative principles of Ronald Reagan.

Schwarzenegger is not the first to put radical rhetoric in the service of moderate policies. His pledge to "lead a movement for fiscal responsibility" echoes the original radical moderate, Ross Perot. Perot also couched his political centrism in anti-establishment language. He too promised to take on both political parties and the powerful interests that dominate them. Perot pledged to return government to the people by relying on "electronic town meetings" in which citizens could directly register their policy preferences without having to rely on their congressional representatives.

Before Perot, anti-establishment rhetoric was the preserve of political radicals. When George McGovern wrested the Democratic presidential nomination from the party establishment, he used the opportunity to promise not only an immediate end to the war in Vietnam but also a massive change in federal income tax designed to redistribute wealth. George Wallace used his insurgency to goad the white working class to rebel against the liberal establishment.

But since Perot, two of the three most important anti-establishment political figures, Jesse Ventura and John McCain, have emulated his political centrism. Although couched in flamboyant and angry rhetoric, their discontent with the status quo has been procedural more than substantive. Ventura may have hoped that his Reform Party would revolutionize Minnesota politics, but he neither promised nor produced any radical change in Minnesota public policy. The centerpiece of McCain's political crusade was campaign finance reform. He was far more committed to changing the way elections were conducted than in changing what government did. Only Ralph Nader has chosen to combine tough populist talk with radical policy change.

Radical moderation has remained in vogue for more than a decade because, indeed, moderate voters are mad as hell. They are furious not so much at how the country is actually governed but at how each of the two parties wants to govern it. They sense that, given the opportunity, the Democrats would embark on costly and intrusive new initiatives, and that the Republicans would so reduce the size and scope of government as to render it inoperative. The biggest political story of the 1990s was the disciplining of partisan political irresponsibility by the moderate electorate. In 1994 it punished President Clinton for his unwieldy health care initiative by electing the first Republican Congress in a half-century. Then, in 1996, it punished the Republicans for their efforts to hamstring the federal government by reelecting Clinton. Because national politics is currently so dominated by the war on terrorism, and moderate voters approve of it, they have so far spared President Bush their ire. Not so in California. Gov. Gray Davis has governed like a partisan Democrat, incurring huge budget deficits and catering to the Democratic Party's congeries of special interests, and moderate voters are threatening to make him pay the price. They could not punish him when he ran for reelection because his opponent, William Simon, was an even more stridently partisan Republican.

Radical moderation remains a potent electoral force, but it is not a recipe for governing. Perot and McCain never got the opportunity to govern as radical moderates. Ventura gave up after only one term. If he wins, Schwarzenegger will discover the sad truth that the people cannot govern, even in the cause of moderation. Any American state, but especially California, is big enough to require that it be governed by elected representatives. Political parties are the only known device for disciplining the behavior of those representatives between elections. One can run against party, but one can govern only by mastering it.

To obtain his policy objectives, Schwarzenegger will need to exploit his personal popularity to make the California Republican Party over in his moderate image and then use it as a political instrument against both conservative dissidents and Democrats. Thus he can succeed only by recognizing that he is not really a radical moderate after all, but a moderate Republican.

The writer is a professor of political science at Boston College and co-author of "Presidential Greatness."