Diane Feinstein, reflecting on the rapid growth in the number of women serving in the Senate during her career at a magazine event honoring women leaders, offered the speculation that if the Senate were all women, financial reform would be done already:
It’s hard to know how to even evaluate that claim, but we can look at the question of what would happen if the 83 male senators all vanished one day and the 17 women ignored quorum rules and rushed ahead on their own. The answer, at least as measured by DW-NOMINATE scores is that the Senate would get much more liberal. The new most-conservative Senator, Kay Bailey Hutchison, is a little bit less-conservative than your average Republican. Susan Collins and Olympia Snowe are the two least-conservative Republicans. Debbie Stabenow of Michigan who’s currently in the most liberal third of the Senate would become the median voter.
Obviously if we did have more women in Congress that’s not precisely how it would turn out. But I do think there’s at least some reason to believe that putting more women in office would per se lead to more progressive outcomes. Considerations of partisanship and local public opinion constrain legislator behavior, but US legislators still operate in a system of comparatively weak party discipline and weak constraints of public opinion (look at how differently Senators Harkin and Grassley represent the same voters in Iowa) so to an extent that’s unusual in the world the actual convictions of rank and file members makes a difference to legislative outcomes. And on average, women are more liberal than men. So I think swapping senators out for same-party women senators might well push things to the left.