The Gateway Pundit provides proof of mail-in ballot fraud in Pennsylvania:
In almost every county throughout the state, the President was awarded a percent of votes 40% less than the percent the President won on election day. If Trump won a county by 80% of the vote on Election Day, he won 40% of the mail-in vote for a county. If the President won 60% of the vote on Election Day, he won 20% of the mail-in vote in another county. This pattern occurred in almost every county with the only noticeable exception of Philadelphia, where the President only earned 30% of the vote on Election Day.