The U.S. Postal Service has adopted a new rule that could create doubt about whether some ballots mailed by voters by Election Day will receive postmarks in time to be counted. A USPS rule that took effect on Dec. 24 says mail might not receive a postmark on the same day the agency takes possession of it. The postal service says it isn't changing its existing postmark practices and is merely clarifying its policy, but some election officials have looked to postmarks as a guarantee that mail ballots were cast before polls closed. The new rule holds implications for 14 states and Washington, D.C., that count ballots arriving after Election Day if they are postmarked on or before that day " commonly called a "ballot grace period." In these states, ballots placed in the mail by voters before the deadline may not be counted if the postal service applies a postmark after Election Day.