But the Nixon example is also a warning. His presidency -- from wage and price controls to the nomination of Justice Harry Blackmun-- could hardly be called a conservative success story. As president, Nixon was a talented man without an ideological compass, mainly concerned with the accumulation of power. Giuliani's 1994 endorsement of New York Gov. Mario Cuomo -- the modern hero of Democratic liberalism -- also indicates some loose ideological moorings. And, as with Nixon, Giuliani's combativeness, on occasion, blurs into pettiness.

Another consequence of a Giuliani victory would be to place the Republican nominee in direct conflict with the Roman Catholic Church. For someone who aspires to be the fourth Roman Catholic to lead a major-party ticket, this is not a minor thing.

Giuliani is not only pro-choice. He has supported embryonic stem cell research and public funding for abortion. He supports the death penalty. He supports "waterboarding" of terror suspects and seems convinced that the conduct of the war on terrorism has been too constrained. Individually, these issues are debatable. Taken together, they are the exact opposite of Catholic teaching, which calls for a "consistent ethic of life" rather than its consistent devaluation. No one inspired by the social priorities of Pope John Paul II can be encouraged by the political views of Rudy Giuliani. Church officials who criticized John Kerry on abortion are anxious for the opportunity to demonstrate their bipartisanship by going after a Republican. Those attacks on Giuliani have already begun.

Across the country, there will doubtlessly be Giuliani Democrats who respond to a culture war against liberalism without the baggage of pro-life moralism. But there will also be Americans influenced by the teachings of John Paul II, who have been persuaded over the years to support Republicans mainly on the pro-life issue. Many are Reagan Democrats. And they will be less impressed by a conservatism purged of pro-life moralism -- which they would see as a purge of compassion and humanity.

These are predictable results if the Republican nominee is not Reagan's heir but Nixon's political twin.