538: Clinton’s Lead Is Becoming Safer

FiveThirtyEight

Gary Johnson averaged just 7 percentage points in 11 polls1 released on Thursday, continuing a string of bad results for the Libertarian Party nominee. At the same time, the number of undecided voters appears to be falling. Those two trends are combining to remove some of the uncertainty in our forecasts — historically, the number of undecided and third-party voters has been strongly correlated with both polling volatility and polling error. The share of voters not supporting the major-party candidates remains higher than it was at this point in the 2012 campaign, for example, but the more it shrinks, the safer Hillary Clinton’s lead becomes.

Clinton and Donald Trump now combine for a little over 84 percent of the vote. That’s the highest their combined share has been since we started issuing our forecasts in June.2 There hasn’t been a huge change, but it’s meaningful.

All this shouldn’t be too surprising. We’re now only about a month away from the election; more voters are making up their minds. In recent elections, moreover, third-party candidates have tended to fade in the polls as Election Day approaches — Johnson and Jill Stein, the Green Party nominee, appear to be following the same trend.

With more voters committed to one of the two major-party nominees, Trump simply has fewer people he can appeal to in order to make up his current deficit, which makes Clinton’s lead more secure. A 5-percentage-point lead with about 15 percent of the electorate undecided or voting for a third-party candidate (about where the race currently stands) is far better than a 5-point lead with over 20 percent of the electorate undecided or voting for a third-party candidate (about where the race was in mid-June). That’s part of the reason that Clinton’s chances of winning the election are in the upper 70s now, while they were in the low 70s back in June.