"Fueling cynicism about the fairness of the electoral process serves to depress voter participation," notes Harvard political scientist Pippa Norris. As evidence she cites the results from the 2012 American National Election Study, which found that 77 percent of people who believe that votes are "very often" counted fairly reported that they voted. By contrast, just 64 percent of those think the process is rigged bothered to cast a ballot. If you think your vote won't count, you're more likely to stay home.
In this election, people who suspect their votes won't count disproportionately favor Trump. According to a September Washington Post/ABC News poll, 46 percent of Americans believe that voter fraud occurs very or somewhat often; for Trump supporters, the number is 69 percent. What's more, Trump needs to attract independent voters to win. But according to the ANES, independents are more likely than Democrats or Republicans to be deterred from voting by claims of electoral unfairness.
Thus, Norris concludes, Trump's claims that the election is rigged will likely "encourage strong Republicans and potential independent supporters to stay home on November 8th." By alleging electoral fraud, "All that Trump is doing is shooting himself in the foot." It wouldn't be the first time.