The conventional wisdom, at least until about four years ago, was that vice presidential selections, even the very good and the very bad, don't end up mattering very much by November. Lloyd Bentsen and Dan Quayle are perhaps the two best examples, the former with poll numbers through the roof (especially after the infamous "Senator, you are no Jack Kennedy" debate) and the latter, well, enough said. From the beginning, Quayle was viewed as a fair or poor choice by a majority of Americans. If it mattered, I might be Justice Estrich, instead of your local columnist.
By that score, the fact that Americans don't know exactly what to make of Rep. Paul Ryan, that the first reaction was decidedly negative (although based on almost no prior knowledge), that my Democratic pals are gleeful, that seniors in Florida are likely to be inundated with old quotes threatening the security of the demographic that would take an ambulance to get to the polls (I ran "Get Out the Vote" in Florida once, believe me), shouldn't matter very much in terms of who wins.
Except that it very well might.
Here's my theory: The whole equation changed with John McCain's selection of Gov. Sarah Palin. Barack Obama's selection of Sen. Joe Biden was the usual non-event. He'd been vetted repeatedly, was known by everybody, could rightly claim the foreign policy experience that Obama arguably lacked, and pleased the convention crowd. Done.