No surprise there: as we have often said, vice-presidential candidates generally have little impact on voter preferences. Thus, the Gallup Poll currently has Obama and Romney tied at 46%/46%, while in Rasmussen’s likely voter survey, with two-thirds of the polling conducted after Romney’s announcement of Paul Ryan as his running mate, Romney continues to lead Obama 47%/44%. So Ryan’s selection has had no measurable positive or negative impact so far.
Again, that isn’t surprising. What cannot yet be measured, of course, is the impact of Ryan’s performance over the rest of the campaign, or the perception that voters will have of Ryan after they learn more about him. For what it is worth, I expect Ryan’s performance to be very strong, and I expect that he will make a positive impression on a large majority of thoughtful voters. I also don’t expect, however, that positive impression to have much impact on the race.