Pennsylvania’s electoral showdown to decide the Republican candidate for the US Senate has reached yet another cliffhanger. The thinly-divided polling numbers officially went into a recount on Wednesday.

Pennsylvania‘s county election boards have been instructed to begin the recount, according to a press release by acting Secretary of State Leigh Chapman. Pennsylvania law requires a recount if the votes tally has a difference of less than 0.5%.

Also Read: What Doug Mastriano’s Pennsylvania win means for the swing state

Celebrity surgeon Mehmet Oz, who is backed by former President Donald Trump, and his Republican rival Dave McCormick currently are separated by a thin margin of 0.1%.

Undated ballots, a minor voter error, might just be the game-changer in the deadlocked race. So far, mailed-in ballots that did not have a handwritten date on the envelope were not counted.

McCormick, roughly a week after the elections, filed a lawsuit that demanded all such ballots be considered in the recounting of votes. Oz challenged McCormick’s lawsuit and said he was “following the Democrats’ playbook”, NBC News reported.

Trump-endorsed Oz currently holds an electoral lead with 902 Republican votes. This means a handful of undated ballots can, once again, swing the election outcome to either side.

The Department of State estimated that counties had about 10,000 provisional and absentee ballots remaining to count, but it did not know how many were cast by Republican voters, according to Associated Press.

Also Read: Why Pennsylvania still doesn’t have a GOP candidate for US Senate

There are another 860 Republican mail-in ballots without handwritten dates on their envelopes that are the subject of court cases, reports citing statements from department officials said.

The winner will face Democratic Lt. Gov. John Fetterman in November’s midterm elections in what Democrats see as their best opportunity to pick up a seat in the closely divided Senate. The incumbent, Republican Sen. Pat Toomey, is retiring after serving two terms.