After a halting start, Paul Ryan delivered a highly effective vice presidential convention speech. It featured not only good lines, but good lines of argument — remind me again why President Obama responded to a financial crisis and a recession with the creation of a new health entitlement? Ryan is not the best natural speaker. But he has an exceptional ability to deliver devastating attacks while seeming entirely innocent. Obama now knows what it is like to be humbled by a high-school valedictorian.

But Ryan’s largest achievement was more subtle and impressive. He managed to make the Obama appeal — so fresh and vivid four years ago — seem used and tattered. And there are few things more damaging in politics than appearing like yesterday’s idealism. Tonight, on the strength of Ryan’s performance, the GOP seemed the party of youth and energy. Such impressions can be reversed, as Democrats will attempt to do next week. But Obama and Biden will need to do some reversing.