Ms. Toretti, Mrs. Rao and other prominent bundlers in both parties said their networks of potential donors, almost exclusively men until just a few years ago, were now composed mostly of other women. And more of them had earned their wealth on their own, in contrast to times when women were more likely to wield their spouses’ wealth or inherited money.

But while women are making more contributions than ever, they still significantly trail men in the magnitude of their giving, with about two-thirds of all the money raised by federal candidates in 2016 coming from men, according to Crowdpac data. Most of the largest overall contributors in the country are men, many of them in fields like energy and finance, where women are still exceedingly rare in corporate boardrooms and executive suites.

Theresa Kostrzewa, a lobbyist in North Carolina who has donated close to $300,000 for Republicans in recent years, described arriving at a gathering for top Mitt Romney fund-raisers in the summer of 2012 at the Deer Valley resort in Utah. The young woman who escorted her to her room, Ms. Kostrzewa recalled, asked her what she did on Mr. Romney’s staff.

“There’s an expectation even among women that other women are not donors,” Ms. Kostrzewa said. “We’re still that much of an anomaly.”

Less visible than the economic inequality that hampers giving by women are the cultural barriers that remain. Some research, for example, suggests that women are more comfortable giving to causes than to candidates, whether out of a sense that politics is grubby or because nonprofit groups will have more impact on the issues they care about.

“If you care about social issues, you may not think that politics is the place to invest your money,” said Debbie Walsh, director of the Center for American Women and Politics at Rutgers University. “You’d rather give to an activist group or a nonprofit.”

Even when women assume senior posts at their companies, they are more reluctant to ask their colleagues for contributions to candidates. Several donors described a familiar worry among their female friends about rocking the boat among male colleagues, or offending people with different political views.