What's the holdup in Pennsylvania's GOP Senate race?

Celebrity doctor Mehmet Oz continues to maintain a narrow lead in the Republican primary for Pennsylvania's U.S. Senate seat following Tuesday's 5pm deadline for counties to report their unofficial results.

• Yes, but: The results aren't final and several issues remain unresolved.

What's happening: Oz remains ahead of former hedge fund CEO David McCormick by 985 votes, or 0.07%, as of Wednesday evening.

• Oz, who was endorsed by former President Trump, has held a razor-thin margin over McCormick for days as mail-in and provisional ballots were counted and printing errors in one heavily GOP county led to delays.

Reality check: The race is likely headed to a recount, which is triggered when the margin of victory is within 0.5%, per state law.

The intrigue: A debate over whether undated mail-in ballots should be counted has thrown the primary into further uncertainty.

• A federal appeals court ruled last week that Pennsylvania mail-in ballots submitted on time without a handwritten date on the envelope last year must be counted.
• The ruling found that the state law's dated envelope requirement was "immaterial," according to the Associated Press.

The latest: Gov. Tom Wolf's administration issued guidance on Tuesday directing counties to count mail-in ballots without dates or with incorrect dates.

• Undated mail-in ballots "should be segregated" out of "an abundance of caution" as a determination about whether to use those ballots to certify the election has yet to be made, according to the guidance.
• It's ultimately up to the state's 67 individual counties to adhere to the guidance.

Meanwhile, McCormick filed a lawsuit in state Commonwealth Court on Monday to require that all counties count undated mail-in ballots.

• McCormick spokesperson Jess Szymanski told Axios that once all Republican votes received on time are counted, they'll unite behind the GOP nominee.

The other side: The Republican National Committee and state GOP are siding with Oz to oppose the counting of undated mail-in ballots.

• The national and state parties plan to intervene against McCormick's lawsuit, RNC chairwoman Ronna McDaniel said in a tweet.
• "Pennsylvania law is clear: undated absentee ballots may not be counted. Changing the rules while votes are being counted undermines the integrity of our elections and sets a terrible precedent for future elections," McDaniel said.