Pennsylvania's Supreme Court ruled unanimously Friday on a key concern surrounding an avalanche of mail-in ballots in the presidential battleground state, prohibiting counties from rejecting ballots because the voter's signature on it may not resemble their signature on their registration form.

HARRISBURG, Pa. (AP) — Pennsylvania's Supreme Court ruled unanimously Friday on a key concern surrounding an avalanche of mail-in ballots in the presidential battleground state, prohibiting counties from rejecting ballots because the voter's signature on it may not resemble their signature on their registration form.

Two Republican justices joined five Democratic justices in the decision.

The verdict was a victory for the state's top election official, Kathy Boockvar, a Democrat who had asked the court to back her up in a legal dispute with President Donald Trump's campaign and Republican lawmakers.

"County 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," the justices wrote.

Trump and former Vice President Joe Biden are locked in a battle to win Pennsylvania's 20 electoral votes.

In her court filing, Boockvar had said that any such rejections pose "a grave risk of disenfranchisement on an arbitrary and wholly subjective basis," and without any opportunity for a voter to verify their signature before their ballot is disqualified.

The decision comes amid a surge in mail-in voting and rising concerns that tens of thousands of mail-in ballots will be discarded in the presidential election over a variety of technicalities.