Initial polls conducted after the Democratic National Convention suggest that Hillary Clinton has received a convention bounce. In fact, it appears likely that Clinton’s bounce will exceed Donald Trump’s, which measured at 3 to 4 percentage points. Thus, Clinton will potentially exit the conventions in a stronger position than she entered them, perhaps also making up for some of the ground she lost to Trump earlier in July. This is good news for Clinton, but we’ll need to wait a few weeks to see if she can sustain her bounce before we can conclude that the race has been fundamentally changed.
Before we continue, a quick note or two about terminology. When we refer to a candidate’s “bounce,” we mean the net gain in her standing in the polls, including changes to her opponent’s vote share. For example, if the previous XYZ News poll had it Clinton 42 percent, Trump 40 percent, and their new poll has it Clinton 44, Trump 39, we’d call that a 3-point bounce for Clinton, since Clinton gained 2 percentage points and Trump lost 1 point.1
Also, when evaluating the gains a candidate has made, it’s important to note when the previous poll was conducted. Based on our models, Clinton led by 6 to 7 percentage points throughout most of June, but her lead dissipated to around 3 percentage points by mid- to late July, just before the conventions. Then, after the Republican National Convention in Cleveland, Trump pulled into an approximate tie with Clinton. It’s those post-RNC polls that make for the best comparison when describing Clinton’s bounce.
So far, however, the post-convention polls have been strong enough for Clinton that there isn’t a lot of need to …