In 2008, Obama received more than 60 percent of the vote among so-called millennials, or 18- to 29-year-olds. Harvard University's Institute of Politics found voters under 30 favor Obama 55 percent to Romney's 36 percent. Maintaining enthusiasm among this voting bloc might be a challenge in Ohio, in part because more than half of 18- to 24-year-olds here aren't in college, and are therefore sometimes harder to reach and motivate. The Obama campaign has tried to counter that by mobilizing thousands of student volunteers to campaign across the state, not just on campuses. Obama has continued to visit Ohio colleges for events and rallies, at least seven since March. Romney has criticized the visits, saying the president would make "promises of free stuff" but hasn't actually created jobs for millennials, as Romney has pledged he will. If he can shave off enough of the youth vote -- which comprised 17 percent of the state's electorate in 2008 -- Romney will be one step closer to taking Ohio.
Left: Ryan arrives at a campaign event at Miami University in Oxford, Ohio, on Aug. 15, 2012.