Polls taken during and after the Republican National Convention, which concluded on Thursday in Cleveland, generally show Donald Trump continuing to gain ground on Hillary Clinton, making for a close national race. But it’s customary for candidates to receive a “bounce” in the polls after their convention. There’s not yet enough evidence to come to firm conclusions about the size of Trump’s convention bounce, but the initial data suggests that a small-to-medium bounce is more likely than a large one.Before we run through the polls, a note of caution: The convention bounce is going to be harder than usual to study this year.