Rejected mail ballots rose in Washington and Oregon following the United States Postal Service changed the rules for postmarking.
The new rule resulted in additional ballots being discounted because of postmarks deemed late.
Lawmakers said that, in several Washington counties, the number of rejected ballots more than doubled following the change.
The increase was linked to the Postal Service's change to how it postmarks mail, affecting voters who mailed ballots on or before the deadline.