My view is that the consensus of evidence so far points toward Mitt Romney having received a small bounce in the polls of perhaps two or three percentage points from the Republican convention in Tampa, Fla.
Oddly enough, however, you can’t really find a poll that seems to reflect a 2- or 3-point bounce exactly. Instead, there have been some polls where Mr. Romney’s bounce has been a bit larger than that, and others where there is little sign of a bounce at all. [cont.]
Nate Silver, New York Times