In 1944 the Minnesota Democratic Party merged with the Minnesota Farmer-Labor Party to form the Minnesota Democratic Farmer Labor Party (DFL), which continues to this day.
The national Democratic Party did not formally adopt this change, but it seems to me that through the 1950s, 60s, 70s there was a de facto coalition of farmers and laborers with the Democratic Party nationally. The Republican Party seemed to identify more strongly with business, banking, and corporate interests.
These affiliations have changed markedly in modern times, most notably in 2016 when Bernie Sanders presented himself as a presidential candidate interested in the common working man, but the Democratic Party elected to go with Hillary Clinton for the national presidential campaign. Fearmongering about wicked "socialism" doomed Sanders and the Republican Party successfully pandered to farmers, laborers, and the rural population, leading to the election of Donald Trump.
A recent article - Democrats’ Long Goodbye to the Working Class - provides more context.
This year, Democrats have chosen to run a campaign focused on three things: abortion rights, gun control, and safeguarding democracy—issues with strong appeal to socially liberal, college-educated voters. But these issues have much less appeal to working-class voters. They are instead focused on the economy, inflation, and crime, and they are skeptical of the Democratic Party’s performance in all three realms.This inattentiveness to working-class concerns is not peculiar to the present election. The roots of the Democrats’ struggles go back at least as far as Hillary Clinton’s presidential campaign in 2016, and, as important, to the way in which many Democrats chose to interpret her defeat. Those mistakes, compounded over subsequent election cycles and amplified by vocal activists, now threaten to deliver another stinging disappointment for the Democratic Party. But until Democrats are prepared to grapple honestly with the sources of their electoral struggles, that streak is unlikely to end...After Sanders unexpectedly came close to tying Clinton in the Iowa caucus, she went on the offensive, seeking to characterize Sanders’s class-oriented pitch as racist and sexist... Trump’s victory was attributable, above all, to the shift of white working-class voters, including many who had voted for Obama, into the Republican column. In the country as a whole, the Republican advantage among white working-class voters went up by six points to a staggering 31-point margin. White college-educated voters went in exactly the opposite direction, increasing the Democratic advantage among these voters by six points.But white working-class voters are far more numerous than their college-educated counterparts, particularly in certain areas of the country, such as the Midwest...The aftermath of the 2022 election will likely give them another opportunity to reexamine their approach. Will they return to their historical roots? Or will their long goodbye to the working class continue?
Lots more at the longread link.