The Pa. Republican Senate primary is heading to a recount with Oz narrowly ahead of McCormick. Here’s what to expect.

Pennsylvania’s Republican Senate primary is headed to a recount.

Acting Secretary of State Leigh M. Chapman announced the recount Wednesday afternoon as celebrity doctor Mehmet Oz maintains a razor-thin margin of fewer than 1,000 votes over former hedge fund CEO David McCormick.

A recount will take several days, but the actual process of counting votes should go faster than it had initially after ballots were cast last Tuesday. Expect the numbers to change slightly — the recount will mean some votes previously read by machines will be reviewed by humans — and for both campaigns to closely watch, and maybe fight over, every vote.

For elections officials, the good news is they have recent experience from when an automatic recount was triggered in November’s statewide Commonwealth Court race, so they know what to expect and how to run the process smoothly.

Here’s what to know about a Pennsylvania recount, based on interviews with lawyers, elections officials, and other experts.

Yes. The secretary of state announced the recount Wednesday afternoon.

Recounts are required by Pennsylvania law, which calls for the secretary of state to order a recount by 5 p.m. the second Thursday after the election.

That is this Thursday. But the secretary has to provide a 24-hour notice to candidates before ordering the recount, which is why the announcement came Wednesday.

A recount is automatically triggered under Pennsylvania law if a candidate’s margin of victory is within 0.5% of the total vote. That threshold is set by a 2004 state law.

In the current GOP Senate primary, Oz and McCormick were separated by fewer than 1,000 votes as of Wednesday morning — less than 0.08% of the more than 1.3 million ballots cast.

Recounts can also be triggered manually, such as by court order or when voters challenge the result. In this case, the statewide recount comes from how close the race is.

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It’s pretty uncommon. The 2004 recount law has only been triggered six times before this one:

Five of the six were judicial races, likely for several reasons, including that there are often multiple candidates who can split the vote, especially when running for multiple seats.

No. The second-place candidate can decline a recount. That request must be made in writing and sent to the secretary of state by noon on the second Wednesday after the election.

Of the six recounts that have been triggered, the candidates in three of the races declined them.

No. The McCormick campaign did not waive the recount, Chapman said.

In a statement Tuesday night, McCormick acknowledged the recount and said he “look[s] forward to a swift resolution so [Republicans] can unite to defeat socialist John Fetterman in the fall.”

» READ MORE: There’s another high-profile vote count in Pa., but Republicans aren’t objecting this time

Pennsylvania doesn’t have runoff elections the way some other states do — the winner of an election is the person who wins the most votes, even if it’s not a majority of them.

That can happen in races with many candidates; for example, the nine-way Republican primary for governor was won by Doug Mastriano with about 43% of the vote.

The recount must be held by the third Wednesday after election day, which in this case would be June 1. The secretary of state said counties can begin as soon as this Friday.

Because Monday is Memorial Day, several county elections officials said they expect to begin next week, perhaps not until Wednesday, which would follow the same timeline as last November.

The recount would need to be complete by noon of the following Tuesday, June 7.

Counties have to submit recount results to the Department of State by noon the next day, June 8, and the secretary then publishes the results.

That means it can take a little more than three weeks after election day for the recount results to be finalized and published. In last fall’s election, the recount was completed and the results were published on Nov. 24, 22 days after the election on Nov. 2.

While the actual final results won’t be in until the end of the recount, counties will report their unofficial tallies beforehand, similar to the usual vote count.

Just like any other time we’re waiting for election results, counties will have different timelines.

That said, counties might not report the results at quite the same pace this time. While election night returns are a constantly rolling feed of results, some counties said they’re planning updates at specific times, perhaps on a regular basis, or maybe even only once they’re done. Still, the individual county-by-county results will start giving information without having to wait for the complete statewide numbers.

It’ll go a lot faster than the initial count. The exact timing depends on the number of votes, the equipment, and the processes, along with some specific questions counties still have — for example, can they first pull out all the Republican ballots so they only have to recount those? Or should they continue keeping those ballots in their current batches, so they end up having to recount all the votes, including Democratic ones?

Still, county elections officials said the process of counting votes should go significantly faster. Some counties were done in a day or two last fall.

“We had ours done in about a day and a half, and we have less ballots this time than we did in the fall,” said Beth A. Lechman, elections director in Centre County. “So I’m anticipating we will definitely be done in a day and a half. … Our plan is, we start June 1 and our results should be available by June 2.”

A lot of the bottlenecks during the vote count won’t exist during the recount.

In the initial count, one of the slowest pieces is that elections officials have to decide whether to count or reject some ballots. Now, those decisions have been already made.

The slow work of reviewing every mail ballot envelope, opening two envelopes to pull out the ballot, unfolding and flattening the ballot, and batching them into groups — all of that’s been done. Mail ballots just have to be run through high-speed scanners.

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In-person election day results actually do take a bit more time. They’re normally the fastest to get added because the machines at polling places tally the votes as they’re submitted throughout election day; at the end of the night, cartridges or USB drives from the machines simply add those totals to the main system. This time, the ballots will be run through scanners to be counted all over again, but those scanners are very fast.

“Smaller counties, as you can imagine, might have that recount done pretty quickly. Larger counties might take longer,” Chapman said. The speed of the count depends on many things, she said, such as the method of counting the votes: “There’s a lot of different factors, from the size of the county to how many resources they have on hand. If counties are able, they can start as soon as Friday.”

The law requires votes be recounted on different machines from the ones they were counted on the first time. (That is, a different type or model of machine, not just a physically different one.)

Normally, in-person results are counted on relatively slow scanners at polling places, while mail ballots are counted on high-speed scanners. During a recount, many counties plan to use their high-speed scanners to run through the in-person results and to use different high-speed scanners for the mail ballots.

They’ll have to carefully track what they use. For example, Philadelphia has two different types of high-speed scanners they use to count mail ballots; they’ll run in-person and mail votes through those scanners, making sure ballots don’t get run through a different system this time around.

Of course, counties don’t just have extra equipment to spare, so they’ll have to buy, lease, or borrow equipment. (In Delaware County, which was already looking into buying faster scanners for a potential recount in November, officials approved the purchase last Friday and two new machines, at a cost of $13,000 total, were expected to arrive Wednesday.)

Running the same ballots through different machines will in some cases return slightly different results, and the numbers will almost certainly shift a bit during a recount.

This is a normal part of a recount process, and it’s part of why recounts happen. There’s a very small amount of error in counting votes because voters don’t submit perfectly clean, precisely filled-out ballots. When the results are close enough that the error can matter, we head to a recount.

Here’s one hypothetical: A voter fills in half a bubble to vote for a candidate, changes their mind and X’s out that vote, then fills in a bubble for another candidate. The ballot scanner reads the original vote, with the X leading it to think that the voter wanted that candidate.

Or in some cases, the original machine flagged it as an overvote in the first place. But voters sometimes choose to submit their ballots anyway, and the race isn’t counted, said Jim Allen, elections director in Delaware County.

During the recount, those ballots get flagged for human review.

The general “voter intent” standard in that case is that elections workers try to determine what the voter meant to do.

It’s possible. As the numbers shift, either candidate could end up adding hundreds or even thousands more votes statewide. That’s not “finding” votes. It’s just part of the recount process.

The candidate who leads in the vote count going into a recount has almost always come out the winner after the recount. None of the previous statewide recounts changed the result. But we’re talking about such a slim margin between Oz and McCormick that it’s certainly possible.

Counties could count votes by hand, but that’s a long and tedious process. Most counties will want to avoid that — the ones they’ll deal with manually are the ones that have to be reviewed to determine voter intent. Otherwise, they’ll use the scanners to move the process along quickly. Counties could choose to count votes by hand if they wish, but they’re not required to.