A design change Pennsylvania officials made to prevent voters from making a disqualifying error on their mail ballots appears to have backfired. The issue — voters failing to write the final two digits of the year on the return envelope — is leading some counties to reject ballots in the primary, despite the state’s new advice to count them.

Last fall, the Pennsylvania Department of State announced it was redesigning the state’s mail ballot return envelope, in part to reduce the number of ballots rejected for lacking a proper date, which is required by law. This year’s envelope has “20” prefilled in the year line and leaves spaces for the voters to fill in the last two digits.

One election director said a “significant” number of voters who returned flawed ballots had not filled in the last two digits of the year, and other election officials around the state echoed that observation. On the Friday before the election, Deputy Secretary for Elections Jonathan Marks sent an email to counties advising them to count ballots even if the envelope lacks the last two digits of the year....

But the department’s emailed advice does not carry the force of law, and counties are making different decisions about whether to count the ballots. Votebeat and Spotlight PA contacted eight counties and found that Philadelphia, Allegheny, and Delaware Counties are counting the ballots, while York, Lycoming, Lancaster, and Snyder Counties are rejecting them. Montgomery County said it would make a decision next week.