Pennsylvania’s Senate race between Dave McCormick and Bob Casey is going to a recount. How will it work?

The Pennsylvania Senate race between Democratic Sen. Bob Casey and Republican Dave McCormick is headed to a recount — a week after the Associated Press called the race for McCormick.

The Pennsylvania Department of State called for the recount Wednesday as Casey and McCormick were separated by less than half a percentage point, the margin for a statewide recount. As of Thursday evening, Casey trailed McCormick by just under 25,000 votes.

This is the eighth time since the automatic recount was made law in 2004 that the law has been triggered, and the fourth time the state has actually entered a recount. Remarkably, McCormick has been a candidate in two of those four recounts, with the most recent one taking place in his Senate GOP primary against Mehmet Oz in 2022, which Oz won by fewer than 1,000 votes.

As counties prepare for the recount in the Casey-McCormick race, they are finishing tallying roughly 80,000 ballots that have not yet been counted in the state. Many of those, however, are provisional ballots that may be rejected.

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 both campaigns are likely to closely watch, and maybe fight over, every vote. But the odds that the result changes in a recount are low.

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

Yes. Secretary of State Al Schmidt announced the recount Wednesday evening.

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.

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.

Casey and McCormick were separated by fewer than 30,000 votes as of Wednesday — less than half a percentage point of the more than 6.9 million ballots cast — which triggered a recount.

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

It’s pretty uncommon. The 2004 recount law has only been triggered seven times before this one, and one of those races featured McCormick:

Five of the seven were judicial races, in which 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 seven recounts that have been triggered, the candidates in three of the races declined them. Casey did not waive a recount, so one will proceed.

The Department of State estimates it will cost about $1 million in state money to administer the recount, which was roughly the cost of the last one.

The recount must be held by the third Wednesday after the election, which in this case would be Nov. 20. Schmidt said counties could begin the recount once they finish tallying remaining ballots.

The recount needs to be complete by noon of the following Tuesday, Nov. 26.

Counties have to submit recount results to the Department of State by noon the next day, Nov. 27, 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.

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.

Counties have to use different scanners from the ones they ran ballots through the first time, so mail ballots will need to go through a different type of scanner than they were initially put through. Some counties already have enough equipment to do this, while others will rent.

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 occurs because of stray markings on ballots from voters that may be flagged by one machine for human review but not another. For instance, if a voter started to vote for one candidate, covered it in an X, and then voted for another, a machine may count the intended vote or spit it out as an “overvote.”

These ballots are then assigned for human review to determine the voter’s intent.

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 afterward.

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

Jonathan Lai is a former Inquirer reporter. This article uses material from his previous coverage explaining the recount process.