Why the smiling, sudden, relentless Sarah Palin should scare Democrats.

The secondary purpose of Palin's speech may be the most important in the long run. She wasn't just launching a new brand (her own). She was relaunching a whole new product: the McCain-Palin ticket. Experience is no longer the central argument. Reform is. McCain and Palin are presenting themselves as leaders who can deliver because they speak and act regardless of the political risk. "Here's how I look at the choice Americans face in this election," said Palin. "In politics, there are some candidates who use change to promote their careers. And then there are those, like John McCain, who use their careers to promote change."

It was a great act—but it was an act, a one-shot show. Palin will have to keep it up for the next nine weeks, when there won't be time to practice or the opportunity to sand down that line to keep it from sounding small and mean. This is a test Obama has already passed. And her sarcasm will wear thin quickly. Reagan could do it because he was a sunny optimist offering a vision of the future. Palin didn't do much of that, other than by offering platitudes (hey, she had a lot of ground to cover).

It's McCain's job to talk about the future Thursday night, say Republicans. He can feel happy that, for the moment, his judgment about his pick seems to have been vindicated. Now he better hope he can do half the job his new sidekick did.