In their book, political science professors Christopher Devine and Kyle Kopko determined that picking a running mate from a key voting bloc probably won’t make a difference with that voting bloc. For example, picking a woman will probably not get you many more votes from women — and picking a popular governor from a certain state will probably not win you many more votes from that state.

But, if 2024 is anything like 2020 or 2016, the margins will only be around 1% and it won’t take “that many more votes” to make a difference here.

“That is a big deal in a closely contested election,” says Dr. John Kennedy, a West Chester University professor of Political Science. “We’re not going to see suddenly Pennsylvania flip so that it’s no longer a battleground but if it does make just even a slight difference, that could be the difference between victory and defeat, not just for Pennsylvania before the entire election.”

The reality is that if you are a Democrat, you would probably already be voting for Harris. So where would those extra votes come from? Former U.S. Congressman Charlie Dent says that some of those votes would probably come from moderate Republicans who don’t like Trump but aren’t crazy about Harris either.

“At this point, if I were advising Harris, I’d say she needs to be ruthlessly pragmatic and do what she must to win Pennsylvania,” Dent told me. “Shapiro clearly helps her in that regard.”

According to Devine and Kopko, the running mate with the best chances of having a positive impact on the election would be an experienced, well-qualified running mate who will make the presidential candidate look better to voters.

Kennedy agrees with that, saying that the primary goal is to “do no harm” to the campaign, pointing to Dan Quayle and Sarah Palin as examples who damaged the chances of their tickets. He adds that Shapiro meets that bar and then some, given his abilities.

“I think if Gov. Shapiro was governor of one of the other states, he still would be viewed as a rising star and a contender,” he says. “Being the governor of Pennsylvania, certainly as a whole different dimension to his potential vote-getting ability.”