This tea-party wave has already crested

The elements of a large GOP victory remain in place. Republican voters are likely to turn out disproportionately. Independents have swung toward the GOP. But through trial and error, Democrats eventually hit on a more effective public message. “They tried bashing Bush for months, which did not work,” Cook explains. “They gave up defending their record. Now they are going after the personal and career shortcomings of their opponents, some of whom are not very well vetted.”

In particular, Cook argues, “Christine O’Donnell gave Democratic voters a bit of a jolt.” The effects of her unique charisma can be found outside Delaware. “Pennsylvania has gotten closer,” says Cook. Republican Senate candidate Pat Toomey “hasn’t done anything stupid. There is spillover from attention to Delaware.”

Tea Party enthusiasm adds to Republican momentum, but clearly some Tea Party candidates are rallying Democratic resistance.