Did Mitt Romney get an electoral bounce from his choice of Paul Ryan as his running mate? Generally speaking, it hasn't seemed so, but Sam Wang thinks otherwise. His model suggests that the Ryan pick did indeed help out Romney for a couple of weeks:
One week after the August 11 VP announcement, I pinpointed the size of the bounce at 1-2 points of swing in opinion. At the two-week mark, the swing has grown to 3-4 points. At the end is an uptick back towards Obama, which suggests that the post-Ryan bounce may have peaked.
In terms of EV, Sam pegs the Ryan bounce at about 40-50 electoral votes. However, "swings in the race are not predictive of the final outcome until the end of September. So the Bain- and Ryan-driven events are of only momentary interest."
I mention this mainly as a counterpoint to people (like me!) who have suggested that the past few weeks have been pretty abysmal for Romney. If Sam is right, that's true, but only until the Ryan announcement, at which point Romney started gaining back some of his earlier losses. Next up are the conventions, which usually produce temporary bounces, and then finally the real campaign. A month from now these temporary shifts in the polls will start to have a lot more meaning.
By the way, Sam says his long-term outlook still has President Obama’s re-elect probability at 88% with a likely electoral outcome of 283-353 EV. So his model overall is more Obama-friendly than most of the others out there.