This article originally appeared here, at wsj.com

Victory has a thousand fathers, but Donald Trump’s 2024 comeback has one cause that outweighs all others and has been underappreciated: the shift in the Latino vote. According to CNN exit polls, Joe Biden outpolled Mr. Trump among Latinos nationwide by 33 points, 65% to 32%. Four years later, Kamala Harris’s lead was only 5 points, 51% to 46%. That 28-point shift is far greater than the move in Mr. Trump’s favor among blacks (2 points) or Asians (12 points), and Ms. Harris actually narrowed Mr. Trump’s advantage with white voters by 2 points.

Latino votes were decisive in most of the states that switched from Mr. Biden to Mr. Trump, and nowhere more so than in Nevada. In 2020, the exit poll found Mr. Biden leading Mr. Trump 61% to 35% among Latinos, who made up 17% of respondents. Four years later, Latinos were 18% of respondents and Mr. Trump led Ms. Harris, 49% to 47%. If we assume the exit polls reflect the actual results, the Latino shift from Mr. Biden to Mr. Trump was 84,188 votes, far in excess of Mr. Biden’s 2020 margin of 33,596.

The effect was less dramatic in Arizona, Georgia and Pennsylvania, but in all those states the change in the Latino vote was sufficient to erase Mr. Biden’s 2020 margin. Even without Michigan and Wisconsin, flipping those four states would have been enough to bring Mr. Trump to 287 electoral votes and victory in 2024.

In Michigan the Latino vote was decisive in a different way. The Latino share of the electorate doubled, from 3% in 2020 to 6% in 2024, and it moved from an 11-point advantage for Mr. Biden (55% to 44%) to a 21-point edge for Mr. Trump (58% to 37%). That adds up to a shift of 89,804 votes—not enough to wipe out Mr. Biden’s 154,181-vote margin in 2020, but more than Mr. Trump’s 80,103-vote edge in 2024.

In other words, while the Latino shift wasn’t sufficient for Mr. Trump to carry Michigan, some improvement in the GOP Latino vote was necessary. That was true in every swing state except North Carolina and Wisconsin. If the Latino vote hadn’t moved, Ms. Harris would have won the election with 293 electoral votes.

Today’s swing states won’t necessarily decide tomorrow’s elections. The exit polls found Florida and Texas Latinos shifting from majority Democratic to majority Republican between 2020 and 2024, diminishing Democratic hopes of eventually flipping those states. CNN didn’t bother polling California and New York in 2024, but both states have large Latino populations, and Mr. Trump narrowed his margin of defeat by nearly 9 points in the Golden State and more than 10 in the Empire State. He still lost both by double digits, but they could one day be competitive.

Latinos are growing in numbers, and unlike black voters they don’t have a 65-year history of supporting Democrats. Neither party should take them for granted.

Mr. Penn was a pollster and adviser to Bill and Hillary Clinton, 1995-2008. He is chairman of the Harris Poll and CEO of Stagwell Inc. Mr. Stein served as New York City Council president, 1986-93.