Check out the WAPO from 2 years ago -- "Could non-citizens decide the November election?"
"In a forthcoming article in the journal Electoral Studies, we bring real data from big social science survey datasets to bear on the question of whether, to what extent, and for whom non-citizens vote in U.S. elections. Most non-citizens do not register, let alone vote. But enough do that their participation can change the outcome of close races. …
How many non-citizens participate in U.S. elections? More than 14 percent of non-citizens in both the 2008 and 2010 samples indicated that they were registered to vote. Furthermore, some of these non-citizens voted. Our best guess, based upon extrapolations from the portion of the sample with a verified vote, is that 6.4 percent of non-citizens voted in 2008 and 2.2 percent of non-citizens voted in 2010.
Because non-citizens tended to favor Democrats (Obama won more than 80 percent of the votes of non-citizens in the 2008 CCES sample), we find that this participation was large enough to plausibly account for Democratic victories in a few close elections."
https://www.washingtonpost.com/news...the-november-election/?utm_term=.7073ede4946b