We don’t know what would have happened in a counterfactual scenario where the popular vote mattered in 2016. Campaigns spend their money trying to turn out voters to win the electoral college, because that’s what counts. That’s especially true of Republicans, whose voters are spread out across rural areas. The smallest PA city Harris visited the last week of the election was Scranton, which has 76,000. In the last week, Trump was in Lilitz PA, which has under 10,000 people. Butler PA has 13,500.

In 2024, Trump made a deliberate play for the popular vote, holding rallies in California and New York City. And there was a major swing in his direction in both states. E.g. Biden won California by 29 points. Harris won California by only 20 points. Trump also targeted immigrant communities in blue states. Biden won foreign born voters by 26 points. Trump won them by 1 point. That swing alone accounts for half the 2020-2024 swing.

It came out later that the internal polling available to both campaigns had Trump ahead the entire time. So he likely felt comfortable taking a risk and spending time in California and New York. But you’ll notice that he parked his surrogates in places like Pennsylvania the entire time. The popular vote has marketing value but it doesn’t count and nobody is trying to win it.