In his detailed article today, New York Times Upshot’s Nate Cohn asks the following:
“Is it possible that the registered Democrats who turned out were Trump supporters, and that the Democrats who stayed home were likelier to be supporters of Mrs. Clinton? Perhaps, but our polling suggests the opposite. In our pre-election Upshot/Siena polls, voters were likelier than nonvoters to support their party’s nominee.”
My preliminary analysis from Florida suggests otherwise. Along with my UF Election Sciences team, we painstakingly collected precinct-level election results for Trump and Clinton by method of voting (early in-person, vote-by-mail, and Election Day) from the nearly 6,000 precincts in Florida’s 67 counties, parsed them and cleaned them up, and then merged the presidential results with precinct information gleaned from the Florida voter file. Since we know which method of voting Florida voters used to cast their ballots, we’re able to make lots of different kinds of precise estimates. One goes to the heart of Nate’s question, at least for Florida.
The plot below shows the proportion of total votes cast on Election Day by White Democrats in each precinct, and the vote share for Trump and Clinton won on Election Day. The horizontal (X-axis) reveals that the range of White Democratic Election Day voters making up a precinct’s total Election Day votes ranges from 0% (e.g., heavily Republican, or Hispanic and Black precincts) to a handful that top 40%.
The precinct dots (weighted by Election Day turnout) and the accompanying lowess fit lines suggest a telling pattern: Trump generally won a greater share of the Election Day vote in precincts where the share of White Democrats exceeded 5% of the total Election Day votes cast on Election day. The greater the share of White Democratic Election Day voters, the greater Trump’s share of the vote.
(This is the identical plot, just with Trump’s precinct vote share overlaying Clinton’s precinct vote share.)
Interestingly, the pattern doesn’t exist for either Early In-Person or Vote-by-Mail votes cast in a precinct by White Democrats (see below), suggesting that some 11th hour surprise (hmmm, I wonder what that could have been, James Comey?), may have influenced the vote choice of White Democrats who waited until Election Day to cast their ballots.