According to a CIRCLE (The Center for Information and Research on Civic Learning and Engagement) at the Jonathan M. Tisch College of Citizenship and Public Service at Tufts University, which conducts research on the civic and political engagement of young Americans, the youth vote influenced 80 electoral votes in the November 6, 2012 election, enough to sway the election results for either candidate. Their research shows that voting maters and even small numbers can and do make the difference. See the full post here on their website.
According to CIRCLE, “EARLY EXIT POLLS: Youth Represent 19% of Voters, Up 1 Point from 2008“, in a survey published by CIRCLE. See full text here.