Two Democratic presidential candidates with national campaign experience are stumbling. A Republican candidate who has run only municipal campaigns is confounding expectations, calling into question some assumptions about Republican voters. Regarding the Republican race, for many months commentators have said that when the Republican base learns the facts about Rudy Giuliani's personal life (an annulled first marriage, a messy divorce, then a third marriage) and views on social issues (for abortion rights, gay rights and gun control, in each case with limits), support for him will evaporate. But such commentary is becoming self-refuting. The insistent reiteration of it during Giuliani's...