The New York Times' Nate Cohn expects Saccone to net roughly 200 votes from the last two Westmoreland precincts. That would give Lamb a lead of about 650 votes. According to CNN, there are about 3,200 absentee ballots in the three outstanding counties (Westmoreland, Greene, and Washington).
To pull ahead, Saccone (based on that hypothetical 650-vote lead) would have to win that pile of absentees by a 60-40 margin. However, he's won the Election Day tally in those three counties by just 56-44. What’s more, absentee ballots in Pennsylvania traditionally favor Democrats, and in fact, they’ve already done so in this race: In Allegheny County, Lamb won the Election Day count by a margin of 15 percent but won the absentees by 24 percent.