Concern has been expressed about illegal aliens and other non-citizens being able to vote because of fraud and the laxity of the voter registration system. But illegal voting is not the main influence that illegal aliens could have on the presidential election and other races.
With the presidential race very close and speculation that the result could be a split between the winner of the popular vote and the winner in the Electoral College, it should be remembered that the Electoral College is composed of electors from each state and that the number of electors is determined by the number of Senate and House seats in each state. The Electoral College gives some added clout to small states because each state has two senators. But the number of votes in the Electoral College that reflects the number of House members for each state is based on the Census count of residents, and that includes illegal aliens and long-term nonimmigrants such as high-tech temporary workers.
What this means is that states that have large concentrations of illegal aliens, like California, get more seats in the House of Representatives and, therefore, also in the Electoral College than they would if the distribution of seats in the House were based on only legal residents or on U.S. citizens or on registered voters.
When we looked at this issue in 2007 based on the 2000 Census, we concluded that California would have six fewer seats in Congress if apportionment were based on the number of U.S. citizens. Nationally, a total of nine House seats would have changed hands. That obviously would have resulted in a similar change in the composition of the Electoral College. In a close election, this much change in the votes in the Electoral College could change the result of an election. The FAIR study can be found here.