The race between Hillary Clinton and Donald Trump has tightened. Clinton, whose lead over Trump exceeded 8 percentage points at her peak following the Democratic convention, is ahead by 4 or 5 percentage points today, according to our polls-only forecast.
The tighter margins in the polls, which reflect a loss of support for Clinton along with a modest improvement for Trump, have come gradually over the past few weeks. The evidence of a tightening has become more widespread, however, and it’s particularly clear in polls that surveyed the race just after the conventions and are retaking its temperature now. Fox News’s national poll, for instance, had Clinton up by 9 points just after the conventions (in the version of the poll that included third-party candidates) and has her up by 2 points now.
There isn’t any guarantee that Trump will continue to gain ground. Over the course of the year, polls have oscillated between showing a dead heat at Trump’s best moments and a lead of 8 to 10 percentage points for Clinton at her peaks. We’re about halfway between those goal posts now. It’s plausible that the recent shift reflects Clinton’s convention bounce wearing off — reversion to the mean — as much as it does momentum for Trump per se. Most importantly, Clinton is still ahead, with a 74 percent chance of winning according to the polls-only model and a 70 percent chance according to polls-plus.
But what if the race continues to tighten? I’ve often heard Democrats express a belief that Clinton’s position in the swing states will protect her in the Electoral College even if the race draws to a dead heat overall. But this is potentially mistaken. Although …