The Pennsylvania Supreme Court ruled in Friday that mail-in ballots cannot be rejected when their signatures don't match voters' signatures on file.
"[C]ounty boards of elections are prohibited from rejecting absentee or mail-in ballots based on signature comparison conducted by county election officials or employees, or as the result of third-party challenges based on signature analysis and comparisons," wrote Justice Debra Todd (D) in the decision.
While the decision was unanimous, there are notably five Democrats and two Republicans on the Pennsylvania Supreme Court.
NEW: The Pennsylvania Supreme Court rules election officials can’t reject mail-in ballots based on signature comparison. pic.twitter.com/41zeIcUP3b— Alex Salvi (@alexsalvinews) October 23, 2020
Mismatched signatures has been the leading cause of rejected mail-in ballots across the country, according to the Philadelphia Inquirer, "and the League of Women Voters of Pennsylvania and Urban League of Greater Pittsburgh had sued the state over counties' use of signature matching, saying it created an unfair patchwork of policies."
That suit was dropped after the Pennsylvania Department of State, which oversees elections, issued statewide guidance to counties that ballots should be counted if they have signatures, without any analysis or comparison.
The Trump campaign challenged that in federal court and lost. -Philadelphia Inquirer
So, it appears that anyone can send a ballot for anyone in Pennsylvania.