Women didn't start voting differently from men until 1980

So what happened? Simply put, prior to 1980, it hadn’t been as clear which party was more naturally aligned with most women’s views on policy issues. But in that election cycle, the Republican Party took a sharp right turn on a number of issues that mattered to women, including issues like spending on the social safety net, the environment, and the role of government. (The GOP also opposed the Equal Rights Amendment for the first time that year in its party platform.) And while a majority of men, who had been increasingly drawn toward the Republicans as the Democrats grew more liberal on issues of race, ended up in Reagan’s column, a majority of women did not.

As the parties became more and more polarized over the next few decades, this gap grew larger too, as women and men’s political allegiances continued to drift apart. “The issues that women tend to care about have largely been embraced by the Democratic Party,” Cascio said.

Other factors may have also helped drive this shift. For starters, several experts told us, women were increasingly likely to join the workforce, particularly in public sector jobs like teaching, which may have reinforced their support for a robust government safety net. At the same time, rising divorce rates, declining marriage rates and changing eligibility requirements for social welfare programs like Medicaid made many women more dependent on government support, which may have also drawn them to the Democratic Party, the party increasingly branded as supportive of big government. And according to a 2017 study, single women are more likely than married women to see themselves as connected to other women, which in turn predicts a more liberal ideology, especially for white and Latina women. (Black women tend to be liberal regardless of their marital status.)

Black women’s support for Democratic candidates was also a crucial part of this shift.