One of the co-authors of a widely cited paper on non-citizen voting writes:
Donald Trump recently suggested that his deficit in the popular vote to Clinton might be due entirely to illegal votes cast, for instance by non-citizens. Is this claim plausible? The claim Trump is making is not supported by our data.
Here I run some extrapolations based upon the estimates for other elections from my coauthored 2014 paper on non-citizen voting. You can access that paper on the journal website here and Judicial Watch has also posted a PDF. The basic assumptions on which the extrapolation is based are that 6.4 percent of non-citizens voted, and that of the non-citizens who voted, 81.8 percent voted for Clinton and 17.5 percent voted for Trump. These were numbers from our study for the 2008 campaign. Obviously to the extent that critics of my study are correct the first number (percentage of non-citizens who voted) may be too high, and the second number (percentage who voted for Clinton) may be too low….
Is it plausible that non-citizen votes added to Clinton’s margin. Yes. Is it plausible that non-citizen votes account for the entire nation-wide popular vote margin held by Clinton? Not at all.
If the percentage of non-citizens voting for Clinton is held constant, roughly 18.5 percent of non-citizens would have had to vote for their votes to have made up the entire Clinton popular vote margin. I don’t think that this rate is at all plausible. Even if we assume that 90 percent voted for Clinton and only 10 percent for Trump, a more than fourteen percent turnout would be necessary to account for Clinton’s popular vote margin. This is much higher than the estimates we offered. Again, it seems too high to be plausible.