WASHINGTON -- Conservatives, who reputedly have lumps of coal where their hearts should be, have fallen in love. So have many people who are not doctrinal conservatives. The world is a sweeter place because Sarah Palin has increased the quantity of love, but this is not a reliable foundation for John McCain's campaign.

The tech bubble was followed by the housing bubble, which has been topped by the Palin bubble. Bubbles will always be with us, because irrational exuberance always will be. Its symptom is the assumption that old limits have yielded to undreamt-of possibilities: The Dow will always rise, as will housing prices, and rapture about a running mate can be decisive in a presidential election.

Palin is as bracing as an Arctic breeze and delightfully elicits the condescension of liberals whose enthusiasm for everyday middle-class Americans cannot survive an encounter with one. But the country's romance with her will, as romances do, cool somewhat, and even before November some new fad might distract a nation that loves "American Idol" for the metronomic regularity with which it discovers genius in persons hitherto unsuspected of it.

McCain should, therefore, enunciate a closing argument for his candidacy that goes to fundamentals of governance, concerning which the vice presidency is usually peripheral. His argument should assert the virtues of something that voters, judging by their behavior over time, prefer -- divided government.

The incumbent Republican president's job approval is in the low 30s but is about 10 points higher than that of the Democratic-controlled Congress. The 22nd Amendment will banish the president in January, but Congress will then be even more Democratic than it is now. Does the country really want there to be no check on it? Consider two things that will quickly become law unless McCain is there to veto them or unless -- this is a thin reed on which to depend -- Senate Minority Leader Mitch McConnell has 40 reliable senators to filibuster them to deserved deaths.

The exquisitely misnamed Employee Free Choice Act would strip from workers their right to secret ballots in unionization elections. Instead, unions could use the "card check" system: Once a majority of a company's employees -- each person confronted one-on-one by a union organizer in an inherently coercive setting -- sign cards expressing consent, the union would be certified as the bargaining agent for all workers. Proving that the law's purpose is less to improve workers' conditions than to capture dues-payers for the unions, the law will forbid employers from discouraging unionization by giving "unilateral" -- not negotiated -- improvements in compensation and working conditions.

Unless McCain is president, the government will reinstate the equally misnamed "fairness doctrine." Until Ronald Reagan eliminated it in 1987, that regulation discouraged freewheeling political programming by the threat of litigation over inherently vague standards of "fairness" in presenting "balanced" political views. In 1980 there were fewer than 100 radio talk shows nationwide. Today there are more than 1,400 stations entirely devoted to talk formats. Liberals, not satisfied with their domination of academia, Hollywood and most of the mainstream media, want to kill talk radio, where liberals have been unable to dent conservatives' dominance.

Today, as usual, but perhaps even more so, Americans are in the iron grip of cognitive dissonance. It is a genteel mental disorder afflicting those people -- essentially everybody -- who have contradictory convictions and yearnings. Consider health care. Americans want 2008 medicine at 1958 prices, and universal coverage with undiminished choice -- without mandatory purchases or government interference with choices, including doctor-patient relationships. As usual, neither party completely pleases a majority of voters. That is why 19 of the 31 elections since World War II produced or preserved divided government -- the presidency and at least one chamber of Congress controlled by different parties.

Divided government compels compromises that curb each party's excesses, especially both parties' proclivities for excessive spending when unconstrained by an institution controlled by the other party. William Niskanen, chairman of the libertarian Cato Institute, notes that in the last 50 years, "government spending has increased an average of only 1.73 percent annually during periods of divided government. This number more than triples, to 5.26 percent, for periods of unified government."

By picking Palin, McCain got the country's attention. That is a perishable thing and before it dissipates, he should show the country his veto pen.