Until the last three weeks before the election, you can safely skip the top-line numbers for every poll you read. That's why I'm less impressed by the president's post-convention "bounce," a term that implies that whatever is up shall come down. Generally, what's more striking is that the president's enthusiasm deficit among self-described independents who tend to vote Democratic has been erased. Those voters are moving (back) into his corner, and they're providing his buoyancy.

Along the same lines, Nate Cohn notices more enthusiasm among non-white voters, who heavily favor Obama.