A group of secret computer scientists and data analysts are reportedly urging Hillary Clinton to push for a recount of the votes in Michigan, Wisconsin and Pennsylvania — three key swing states that delivered Donald Trump the presidency on Election Day. According to New York Magazine, that group claims it has found evidence of vote tampering and wants Clinton’s camp to file to recount all those millions of votes.

There’s no evidence the Clinton campaign is actually considering such a drastic move. And indeed, New York says the White House is discouraging her campaign from trying. But if it were to, Pennsylvania would likely be the campaign’s biggest hurdle.

A recount in Pennsylvania would be, as described here by an expert on voting machines, a “nightmare scenario.” The Keystone State’s voting machines are outdated by decades and don’t create any sort of paper trail that can be used in cases of recounts.

A recount could still happen under court order. But it would be unprecedented in recent history in Pennsylvania. Though statewide recounts have taken place here, they’ve been ordered by the Secretary of State in Pennsylvania and were mandatory under state law because the winner of the election won within a margin of 0.5 percent. That’s not the case here — Clinton lost to Trump in PA by about 70,000 votes, more than a full percentage point.

Massive voter fraud in the state would have to be proven for Pennsylvania to be overturned or invalidated. And if Clinton’s camp claimed that was the case, it would be using the exact tactic Trump memorably stumped on. Voter fraud is still not common, and Trump was wrong when he implied Pennsylvania was a breeding ground for it. Clinton would be, too.

Feasibility of a Pennsylvania recount

Remember when Florida recounted in 2000, and there were all those photos of poll workers diligently analyzing paper ballots by hand? That wouldn’t happen in Pennsylvania. More than 80 percent of voters cast their ballots on a voting machine with no receipts and no paper ballots, making a recount that much more of a mess.

The mere thought of a recount taking place in Pennsylvania is probably making a lot of people cringe right now. It’s a long, cumbersome process that could cost taxpayers hundreds of thousands, if not millions, of dollars. Pennsylvania is one of just a handful of states that has a fully computerized voting system without a paper trail.

“The nightmare scenario would be if Pennsylvania decides the election and it is very close. You would have no paper records to do a recount,” Lawrence Norden, the co-author of a report on told voting machines, told the Los Angeles Times.

Most swing states have voting systems that do have a paper trail. More than 80 percent of voters nationwide used a voting machine with a paper trail on Nov. 8. But not in Pennsylvania! It’s one of 15 states with no mandatory paper trail. When concerns about election fraud were (somewhat ironically, now) raised by Trump ahead of the election, some analysts said Pennsylvania would be smart to implement a backup system of paper ballots should a recount be granted. That didn’t happen.

So if a recount were to be ordered by a court in the state, it would be a massive undertaking, as every voting machine in the state’s more than 9,000 voting divisions would have to be opened and re-analyzed. There’s no Pennsylvania law that requires this be done in public, but every candidate or an attorney representing said candidate is allowed to be present for a recount.

If there are allegations of voter fraud related to the machines themselves, every one would have to be checked and re-checked, and it’s not entirely clear under Pennsylvania law what the threshold is for the amount of voter fraud that would lead to invalidated election results. On top of that, there’s almost no way every machine could have been tampered with, as election officials in the state say they’re safe because they’re so outdated and aren’t hooked up to the internet.

If the Clinton campaign were even considering what this group of analysts says it’s urging them to do, Pennsylvania’s antiquated system would likely be at the top of the campaign’s list of nearly-impenetrable challenges. It’s a list the Clinton campaign would also have to weigh quickly.

The deadline to file for a recount in Pennsylvania is 20 days after the election: Monday, Nov. 28.

How to get a recount

The most common way to get a vote recount in Pennsylvania is through an order by the Secretary of State, which is mandatory by law in statewide races decided by less than half a percentage point. That can’t happen in this case.

There are two other ways to get a vote recount. Voters can initiate a recount by having three voters from a voting district in question petition the county and ask for a recount. Coordinating that statewide would be nearly impossible. The third way, and the most likely in this case (if you can even called it “likely”), would be initiated by the candidate.

A candidate can’t actually file for a vote recount under Pennsylvania law. Instead, they would have to challenge a county board regarding its vote computations, and a state appeals judge would have to rule that a statewide recount is necessary. That means the Clinton campaign would either have to request a recount by petition in every voting district or present a prima facie case showing voter fraud. (Prima facie is a lower threshold than beyond a reasonable doubt. A judge would just have to rule that fraud probably occurred in order to call for a recount.)

Leading up to the election, it was Trump and his supporters who faced criticism for claiming this could happen in Pennsylvania. The president-elect, just weeks before the election, told a crowd in Altoona that the “only way” he could lose Pennsylvania is if “cheating” went on. Voter fraud is generally uncommon, and voting irregularities that do occur are often the result of clerical errors that wouldn’t add up to amount to 70,000 votes.

The Clinton campaign would have to present the equivalent of probable cause evidence showing something much more sinister.

It’s very, very unlikely to be overturned

Recounts are rare, and cases where the original result is not sustained are even rarer. A 2011 analysis found that over the previous decade, there were 18 statewide recounts out of 2,881 state general elections. Those recounts resulted in just three reversals: A 2008 Minnesota Senate race, a 2006 auditor race in Vermont and a 2004 gubernatorial race in Washington.

There were two statewide recounts in Pennsylvania recent memory, one in 2009 and another in 2011. In 2009, a mandatory statewide recount was ordered (because of that 0.5 percent threshold) in the primary race for Commonwealth Court. The original result was sustained, and the recount cost taxpayers more than half a million dollars. In 2011, there was a primary recount for the Superior Court under the same conditions. That result was also sustained.

What should be most troubling for Clinton supporters who want her to ask for a Pennsylvania recount is that in the past, these recounts have yielded a shift of just a couple hundred votes, certainly not enough to overturn anything in Pennsylvania. Clinton’s team would have to rely on proving massive voter fraud enough for a Pennsylvania court to rule the entire state invalid — an unprecedented and nearly impossible feat.