Alexandria Ocasio-Cortez, the new poster child for the progressive movement, who shocked the nation by clobbering a 10-term incumbent in her New York-area district Democratic primary, has been a woman on a mission. While she is still technically one of hundreds of congressional candidate who need to run and win in November, Ocasio-Cortez has lately spent more time on the trail for progressives in other parts of the country.

While the 28-year-old political newcomer insists she isn’t the spokesman of the Democratic Party’s ascendant grassroots progressive wing, she has acted as though she is. Congressional candidates usually don’t endorse insurgents against establishment Democrats; after all, who wants to ruffle the establishment’s feathers when you have to work them if the voters send you to Washington? Yet Ocasio-Cortez has been crazy enough to do just that, backing challengers to sitting Democratic incumbents in Florida, Massachusetts, Delaware, and Maryland.

Endorsing is one thing, but getting your endorsements across the finish line is very different. The former is painless; the latter impossible if registered Democrats are uncomfortable with the candidate or message. Ocasio-Cortez and her mentor Senator Bernie Sanders learned this the hard way during this week’s volley of Democratic primaries. The progressives and Democratic Socialists may be loud and fired up, but they haven’t yet had much success at winning against the establishment wing of their party.

Even before Tuesday’s contests, the progressive bark was worse than its bite. According to a Brookings Institution analysis, only about 22 percent of candidates who identify as progressives have won their elections against the establishmentarians this year. This week didn’t help the ratio. Abdul el-Sayed, the 31-year-old physician who was looking to become America’s first Muslim governor, got clobbered in his Michigan primary. Cori Bush, another candidate Ocasio-Cortez stumped for, lost her primary to incumbent William Clay by around a 19-point margin. And Brent Welder, whom Sanders and Ocasio-Cortez both flew to Kansas to campaign for, lost by 2,088 votes to Sharice Davids. While Davids is anything but a centrist, her victory helped expose what some House Democrats have already said publicly: much of the party isn’t necessarily ready for the big, bold, uncompromising resistance dogma that the progressive movement advocates for.

Do Tuesday night’s results mean the progressive moment has come and gone? Absolutely not. Political parties are not defined by one spate of primary contests, and suggesting otherwise is disingenuous. In many ways, the Bernie Sanders wing of the Democratic Party has already won by stamping the party platform with ideas that never would have been accepted even a decade ago. A $15 national minimum wage, universal government-supported health care, the demonization of corporate money, and the abolition of the Immigration and Customs Enforcement Agency—positions that party leaders wanted to and have tried to marginalize—have become mainstream. If Bernie Sanders hadn’t run such a passionate presidential campaign in 2016, progressives wouldn’t be where they are today.

What Tuesday’s results do show, however, is that there is no one-size-fits-all solution for the Democratic Party. Ocasio-Cortez may seriously believe that her New York City district is not all that different from the Midwest or red America. But if the post-2016 political era has taught us anything, it’s that betting on the Sanders model as a winning horse nationwide is a grave and self-defeating error. It may work brilliantly in the Bronx, Seattle, Los Angeles, and other urban areas, but it’s unlikely to be effective in the very districts Democrats need to retake the House majority.

Democrats have a great chance at winning the midterm elections this November. The way to success, however, is by nominating candidates who fit the political, cultural, and economic characteristics of the districts they are running in, not by insisting that the entire country is ready to stampede to the left.

Daniel R. DePetris is a foreign policy analyst, a columnist at Reuters, and a frequent contributor to The American Conservative.