Pennsylvania’s state Supreme Court is weighing in on a flashpoint amid ongoing vote counting in the U.S. Senate election between Democratic Sen.

The Pennsylvania Supreme Court on Monday rebuked Democratic-controlled elections boards that counted undated and misdated mail ballots, siding with Republicans and reiterating that such votes are invalid.

The Keystone State's top court reaffirmed that certain mail-in ballots cannot be counted, in a blow to certain Democrat-led counties.

The Pennsylvania Supreme Court has directed county officials not to count mail ballots for the general election that arrived on time but in envelopes missing the correct date handwritten by voters.

The Pennsylvania Supreme Court on Monday forbade counties from counting misdated or incorrectly dated mail-in ballots — which election boards in Bucks and Montgomery counties and Philadelphia had voted to accept.

Court's order was in response to petitions filed by Republican National Committee over attempts by some county board of elections to flout the state's election law and prior court orders. More than one thousand ballots were at stake in the offending counties.

The Pennsylvania Supreme Court ruled Monday that mail-in ballots in the Nov. 5 election that lacked handwritten dates or were improperly dated on their outer envelopes as required under state law cannot be counted.