A study in 2014 in the online Electoral Studies Journal claimed: In the 2008 and 2010 elections, as many as 2.8 million illegal noncitizen votes were cast, "enough to change meaningful election outcomes including Electoral College votes and congressional elections," said the study, authored by Jesse T. Richman and Gushan A. Chattha, both of Old Dominion University, and David C. Earnest of George Mason University.
The bombshell was this: "Noncitizen votes likely gave Senate Democrats the pivotal 60th vote needed to overcome filibusters in order to pass health care reform and other Obama administration priorities in the 111th Congress."
https://ww2.odu.edu/~jrichman/NonCitizenVote.pdf
https://www.washingtontimes.com/news/2017/jun/19/noncitizen-illegal-vote-number-higher-than-estimat/