Senator J.D. Vance, who joined former President Donald J. Trump’s 2024 ticket on Monday, once described his new running mate as a kind of “cultural heroin” — and privately feared that he could be “America’s Hitler.”

That was nearly a decade ago, when Mr. Trump’s political ascent coincided with Mr. Vance’s rise as the author of “Hillbilly Elegy,” his memoir of growing up poor in rural Kentucky and Ohio. Mr. Vance was frequently interviewed for his views on the white working-class communities described in his book, full of the types of voters drawn to Mr. Trump’s “Make America Great Again” pitch, and to his insistence that he alone could save a nation in decline.

In a 2016 article in The Atlantic, “Opioid of the Masses,” Mr. Vance wrote: “During this election season, it appears that many Americans have reached for a new pain reliever.” He went on: “It enters minds, not through lungs or veins, but through eyes and ears, and its name is Donald Trump.” But, he argued, Mr. Trump was not the solution.

Times change.

By 2018, Mr. Vance’s stance had softened, as he viewed Mr. Trump as speaking, if coarsely, to the frustrations of the people he had written about. By 2022, when Mr. Vance was running for Senate in Ohio, the self-described “Never Trump guy” from six years earlier received a race-changing Trump endorsement.

Here is a look back at Mr. Vance’s MAGA evolution.

‘Hillbilly Elegy’

Mr. Vance’s memoir drew critical acclaim. Well-timed for the 2016 election, it made best-seller lists and was frequently hailed as a must-read for Americans seeking to understand Mr. Trump’s support from white working-class voters.