But I also think that if a single bold thread runs through the results so far and the surprisingly strong general-election prospects of some Democratic nominees in districts and states that lean Republican, it’s not a given position on Medicare for all or the Immigration and Customs Enforcement agency. It’s candidates’ ability to connect and make the case.

Did Andrew Gillum, the Democratic contender for governor in Florida, win his primary because he was the most progressive of the four main candidates? That’s a less likely explanation than two others. First, his rivals, fixated on each other, competed for and split the same territory, enabling Gillum to gobble up different ground. Second, he was an impassioned, magnetic competitor with an inspiring biography, a talent for telling it and an innovative approach.

That same description fits Ocasio-Cortez and also Ayanna Pressley, whose recent victory over a longtime incumbent, Representative Michael Capuano, in a Democratic House primary in Massachusetts was another of 2018’s big stories. Ocasio-Cortez and Pressley outsprinted, outsmarted and outtalked their opponents. So did Stacey Abrams en route to her historic triumph in Georgia, where she became the first African-American woman to be nominated for governor by the Democratic Party.