Democrats have regularly argued that, with a robust populist pitch, winning back white working-class voters could be within reach.

In 2016, there is evidence that, with the impact of Donald J. Trump on the race, that could actually happen.

In the past, Republicans could appeal to both more tolerant and intolerant white working-class voters through “dog whistles.” But if Mr. Trump is the Republican nominee, his open appeal to racial and xenophobic sentiments — calling for the deportation of Latino immigrants, barring Muslims from entering the country and flirting with white supremacists — could push at least some part of the tolerant sector to the Democratic side.

Meanwhile, Democrats are going after that more tolerant sector with a progressive populism initially and charismatically championed by Bernie Sanders but increasingly advocated by Hillary Clinton as well.