The Pennsylvania Senate race between Democrat incumbent Bob Casey and Republican Dave McCormick is headed for a mandatory recount, and the Casey campaign is challenging several counties that rejected ballots from unregistered voters.

The race was already called by the Associated Press in favor of McCormick, and McCormick’s team says the numbers show Casey has no path to victory.

The Pennsylvania Department of State announced the recount Wednesday because the results are within a half percent margin, with McCormick ahead by 27,000 votes.

A new timeline now takes over before the results can be certified.

“Once counties finish counting their ballots, they must begin the recount no later than Wednesday, Nov. 20. They must complete the recount by noon on Nov. 26 and must report results to the Secretary by noon on Nov. 27. Results of the recount will not be published until Nov. 27,” Pennsylvania Secretary of State Al Schmidt said in a statement.

Schmidt said Wednesday that county election officials reported 60,366 uncounted provisional ballots and 20,155 uncounted mail-in and absentee ballots. “That 80,521 total includes all ballots for which county boards of elections have not yet made a final resolution regarding their validity or eligibility to be counted.” Schmidt said.

The 80,000 remaining votes mentioned by the Department of State in its statement include the 10,000 that were added to the totals Wednesday, Harris said, and tens of thousands of ballots have been adjudicated as invalid by the counties.

Mark Harris, lead strategist for the McCormick campaign, said in a Thursday media call that Casey’s campaign has sent letters to some counties challenging their rejection of provisional ballots because the voters were “determined by the Board not to be registered.”

“CFS [Casey For Senate] challenges the rejection of provisional ballots based solely on the Board’s staff’s failure to find voters’ names on registered-voter lists,” one of the letters says.

“The Casey position is that they are the ones who need to confirm whether a voter is registered or not, not taking the word of the local board of elections and the [Pennsylvania computer voter registration system.]” The McCormick campaign’s attorney James Fitzpatrick said on the call.

McCormick’s campaign will go to court to prevent the provisional ballots of unregistered voters from being counted.

“There is zero legal precedent to count the votes of unregistered voters in Pennsylvania,” Fitzpatrick said. Pennsylvania law requires that in order to cast a ballot, you must be registered.

In another case, McCormick’s team will ask the state Supreme Court to affirm its decision directing counties not to count mail ballots that do not have a date written on the envelope by the voter. This is a requirement of mail votes according to Pennsylvania law, but some counties have indicated that in this election, they will count the undated ballots anyway.

The Casey campaign could not be reached for this story. It is using the recount as a vehicle for fundraising.