Women are more Democratic than men, and younger voters are more Democratic than older ones. The former has been true for decades, and the latter is a trend that’s at least 10 or 15 years old. But a new Pew survey using a huge sample to allow for insight into demographic details shows that the intersection of these two trends is staggeringly large.

Among millennials, which Pew identifies as people born between 1981 and 1996, men lean toward Democrats by 8 percentage points — far and away a bigger tilt toward Democrats than older cohorts of men. But millennial women favor Democrats by a staggeringly large 70-23 margin.

That means that even as millennial men are the most Democratic-friendly cohort of men, the millennial gender gap is also by far the largest of any cohort. In the Silent Generation, women are 8 points more favorable to Democrats. Among boomers, it’s 10 points. Among Gen-Xers, it’s 11 points, and among millennials, it’s 21 points.

That’s driven by what seems to be an explosive change in millennial women’s political sentiments over just the past two or three years even while most other groups’ views have stayed relatively stable.

Young people are, of course, notoriously fickle midterm voters. So how much this shift in sentiment is translated into a shift in actual policy outcomes will hinge, critically, on whether this big bloc of younger women shows up in November. But it’s fair to say that while a certain amount of gender polarization is nothing new to the political system, the scale that we are now witnessing among younger people is unprecedented.