As I noted on Saturday, past vice-presidential announcements have typically been greeted with a small “bounce” in the polls. Harry J. Enten, at The Guardian, has run the numbers on this for vice-presidential announcements dating back to 1984. He finds a net gain of four percentage points in the polls — and a mean of six — for the party that just named its new running mate.
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Now we’re looking only at the vice-presidential candidates who were named before either party’s convention, as Representative Paul D. Ryan just was.
We see a median bounce of three percentage points, and an average of five, with Mr. Lieberman and Mrs. Palin eliminated.
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So there’s something of a consensus in the polls, showing a net gain for Mr. Romney of between zero and two percentage points since the announcement of Mr. Ryan.
538: The fog of polling and ryan's bounce so far
The Ryan pick may turn out to have been brilliant for some other reason, but right now it is looking like a flop. The top of the ticket remains Romney; he remains aloof, secretive, arrogant, unlikeable, and entitled. And Ryan comes with the baggage of his murderous budget and his extreme positions on social issues.
Obama is winning. All he has to do is grind, and he knows how to do that very well.