TOPEKA, Kan. (AP) — The head of the U.S. Postal Service expressed frustration Thursday with ongoing criticism by election officials of how it handles mail ballots while also seeking to reassure voters that it's ready to handle an expected crush of those ballots this fall. U.S. Postmaster General Louis DeJoy told reporters that it's difficult for the Postal Service to address “generalities” about perceived problems and said some election officials don’t fully understand its efforts to deliver ballots in time to be counted.