Registered voters who stayed home probably cost Clinton the election

Given how closely party identification tracks with vote choice, the disparity in turnout probably cost Clinton the election. SurveyMonkey did not ask non-voters whom they would have voted for, but we do know that more than 90 percent of self-identified Democrats who cast a ballot voted for Clinton and more than 90 percent of Republicans voted for Trump. Moreover, voters who didn’t identify with or lean towards either party were slightly more likely to prefer Clinton to Trump. That means that had the non-voters cast a ballot in accordance with their party identification, Clinton’s advantage over Trump nationally would have expanded by about 2 to 3 percentage points. That almost certainly would have been enough to flip enough states for her to win the Electoral College.

The large gap in party identification between registered voters who cast a ballot and those who didn’t also helps to explain why pre-election polling underestimated Trump. Pre-election polls suggested that the gap between these two groups would be smaller than in 2012; the SurveyMonkey data suggests it was larger.

The biggest reason given by non-voters for staying home was that they didn’t like the candidates.2 Clinton and Trump both had favorable ratings in the low 30s among registered voters who didn’t cast a ballot — both had ratings in the low 40s among those who did vote. That’s a pretty sizable difference. So why was Clinton hurt more by non-voters? Trump was able to win, in large part, because voters who disliked both candidates favored him in big numbers, according to the exit polls.