Something peculiar has happened. As I write, none of the Republican candidates for Senate has become a public embarrassment. On the contrary: For the first time in a decade, it is the Democratic candidates, not the Republican ones, who are fodder for late-night comics. That the Democrats are committing gaffes and causing scandals at a higher rate than Republicans not only may be decisive in the battle for the Senate. It could signal a change in our politics at large.