Up to 70% of vote this November could be cast by mail. But not all states will allow it. And a recent NPR survey found that 65,000 absentee or mail-in ballots have been rejected this year for being late.NPR's Mary Louise Kelly visited a county in Pennsylvania to see what challenges lay ahead for election night in a critical swing state. Find and support your local public radio station.Email us at considerthis@npr.org.