Could non-citizens decide the November election?

Could control of the Senate in 2014 be decided by illegal votes cast by non-citizens? Some argue that incidents of voting by non-citizens are so rare as to be inconsequential, with efforts to block fraud a screen for an agenda to prevent poor and minority voters from exercising the franchise, while others define such incidents as a threat to democracy itself. Both sides depend more heavily on anecdotes than data.

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. Non-citizen votes could have given 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. Sen. Al Franken (D-Minn.) won election in 2008 with a victory margin of 312 votes. Votes cast by just 0.65 percent of Minnesota non-citizens could account for this margin. It is also possible that non-citizen votes were responsible for Obama’s 2008 victory in North Carolina. Obama won the state by 14,177 votes, so a turnout by 5.1 percent of North Carolina’s adult non-citizens would have provided this victory margin...

Finally, extrapolation to specific state-level or district-level election outcomes is fraught with substantial uncertainty. It is obviously possible that non-citizens in California are more likely to vote than non-citizens in North Carolina, or vice versa. Thus, we are much more confident that non-citizen votes mattered for the Minnesota Senate race (a turnout of little more than one-tenth of our adjusted estimate is all that would be required) than that non-citizen votes changed the outcome in North Carolina.

Our research cannot answer whether the United States should move to legalize some electoral participation by non-citizens as many other countries do, and as some U.S. states did for more than 100 years, or find policies that more effectively restrict it. But this research should move that debate a step closer to a common set of facts.