(NewsNation) — The highly contested Senate race in Pennsylvania between Democrat John Fetterman and Republican Mehmet Oz is neck-and-neck with Oz at 47%, just 0.1% ahead of Fetterman at 46.9%, according to the latest Real Clear Politics polling average.

This comes as the Fetterman campaign sent out a memo to supporters Monday warning of potential efforts to discredit results. The memo touched on the timing of election results in Pennsylvania, suggesting new GOP laws that early and mail-in ballots can’t be counted until election morning are “an intentional move to help Republicans sow doubt on the election results when it suits them.”

The state Supreme Court also recently ruled ballots not properly filled out would be set aside and not counted. Nearly 3,400 people in Philadelphia were informed over the weekend their vote may not count.

Historically, day-of voting totals tend to show more Republican support, whereas early and mail-in ballots show more Democratic support.

The winner of the race could help determine which party controls the Senate.

Each campaign has spent nearly $200 million trying to court voters in the Keystone State. That dollar amount also underscores the importance of the race.

“I’m running to serve Pennsylvania. Oz is running to use Pennsylvania,” Fetterman said.

Both Fetterman and Oz campaigned to the very end, including over the weekend when they spoke directly to their supporters.

“I will bring change to Washington so they treat us the way we deserve,” Oz said.