Pennsylvania

This is not the fault of the County Election Board, nor is it the US Postal Service's fault. The contractor is the printing company that provided matched mailing services and they are responsible for doing it right. The customer - in this case it's the county election board - provided a datafile with all of the name/address data and their responsibility is to check the data before it is given out.

Matched mailings are a standard program and the company that won the contract was responsible to see that it was done correctly. They have the liability here, the contractor should cover all the costs associated with replacing the incorrect ballots with correct ones.

Whether there was an underlying political motive in play would be a separate issue.