“Women like me aren’t supposed to run for office,” Alexandria Ocasio-Cortez declared in the opening of her campaign video that went viral this spring. And women like her weren’t supposed to win primary challenges against incumbents, particularly powerful ones like Representative Joseph Crowley, who had been mentioned as a potential House speaker.

But she did. So is this the year that women break the rules — and win?

This year’s midterm elections have produced a surge of women like her across the country: progressive candidates running outsider campaigns powered by strong personal narratives and women’s activism that began with massive marches the day after President Trump’s inauguration and has grown through protests against gun violence, the stripping away of the Affordable Care Act and immigration policies that divide families.

But Ms. Ocasio-Cortez’s win in New York’s 14th Congressional District Tuesday may be more one-off than wave. The same night she won by 15 points, another woman of color, Saira Rao, lost her energetic bid from the left in a primary against Rep. Diana DeGette in Colorado. Three weeks earlier, so did another, Tanzie Youngblood, in an open primary against a conservative Democrat in New Jersey.