The looming battle is critically important to correct two long-standing electoral dilemmas for each party. For Republicans, winning strong support from married women means they could close the gender gap, a problem that plagued them during President Obama’s 2012 reelection campaign. For Democrats, the goal is to ensure that single women, who are solidly Democratic, turn out to vote in the first place. Like other core members of the party’s coalition, they vote in dramatically smaller numbers during midterm elections.

The political difference between married and unmarried women is stark. In 2012, Obama won unmarried women better than 2-to-1 while losing their married cohorts, who voted 53 percent to 46 percent for Mitt Romney. The split stems from a variety of reasons. Single women, for instance, are more attuned to debates over access to contraception—a key Democratic talking point against Republicans in recent years.

But according to pollsters, the gap is rooted mostly in economics. Single women, especially those with children, tend to be poorer than married women, many of whom live in a two-income family. The difference in financial circumstances fundamentally alters how each views government assistance.

“Women in a stable marriage, whether a single- or double-income household, they have a support structure that’s kind of built in,” said Wes Anderson, a Republican strategist who has studied the split between the two blocs. “And they start to become more conscious about what they’re paying for with other people, so they tend to gravitate toward us.”