A stunning upset win against a longtime Democratic incumbent in the New York primaries has many talking about a "Democratic Spring."

Democratic strategists say Alexandria Ocasio-Cortez — the 28-year-old who beat the longtime incumbent Rep. Joe Crowley — is a case study in the kind of insurgent Democrats who could lead a 2018 "blue wave."

On Tuesday night, the impossible happened in New York City.

Alexandria Ocasio-Cortez, a 28-year-old self-described socialist, unseated Rep. Joe Crowley, one of the most powerful and entrenched Democrats in Congress.

A few congressional districts away, in Brooklyn, Adem Bunkeddeko, a young community activist, came just 1,000 votes away from beating the veteran incumbent Rep. Yvette Clarke. And Rep. Carolyn Maloney, who represents a stretch of affluent communities across three boroughs, was challenged by another young candidate of color, Suraj Patel.

Some Democratic strategists say that Ocasio-Cortez's stunning primary victory reflects a new energy among the party's base — and that if a so-called blue wave comes in November, she and the other insurgent progressive candidates across the country will be the reason.

Women of color are leading the wave

Democratic women and women of color are running for office in historic numbers this year. And of the 293 women who have run or are running as challengers for the House or the Senate, 34 are taking on Democratic incumbents, according to the Center for American Women and Politics at Rutgers University. Women of color — many of whom have deep ties to their districts and states — are among the most promising candidates.

"The way you take over the Democratic Party is you support progressive women of color who know how to f---ing organize. Everything else comes second," Sean McElwee, a progressive activist and pollster, tweeted on Tuesday.

Amanda Litman, a former Clinton campaign staffer who cofounded Run For Something, an organization that helps young Democrats run for local office, says Ocasio-Cortez's win illustrates that the party is taking women of color seriously — as both voters and candidates.

"Women of color are the backbone of the Democratic Party, and our leaders should be representative of the voters we're trying to reach," Litman said.

Jesse Ferguson, a Democratic strategist who served as a spokesman for Hillary Clinton's 2016 campaign, said candidates like Ocasio-Cortez drew a helpful contrast with President Donald Trump and his administration.

"What are the American people seeing in the last two weeks?" Ferguson said. "Donald Trump saying that young women of color should be in cages on the border and Democrats saying young women of color should be in Congress."

Demographic shifts

Some say the changing demographics of New York voters — and Democratic voters across the US — will be key in the 2018 midterms. And new voters, many of whom may also be new Americans, don't have allegiances to incumbent Democrats.

"It's more important than ever before to know who the new voters are," said Stu Loeser, a veteran New York Democratic strategist. "Personally, in the last year I've twice been in rooms where I knew everyone was a citizen — a passport office in Lower Manhattan and at jury duty in the Bronx — and most people appeared to be new Americans."

Loeser pointed out that the makeup of large swaths of New York City, including the 14th District in the Bronx and Queens, where Ocasio-Cortez won, have changed dramatically since Crowley took office in 1999. Queens, he said, has gone from "a predominantly white, largely Jewish and Catholic borough to the most diverse county in the world." The 14th District, where Ocasio-Cortez was raised, is now about 50% Latino and over 80% nonwhite.

Jon Reinish, a Democratic strategist and former aide to Sen. Kirsten Gillibrand of New York, said the New York upset sent a message to all establishment Democrats to stay in touch with their constituents.

"If you want to continue to win, you better look really, really hard at your district — and never, ever lose touch of where the energy is," Reinish said. "You can't rely on where the energy has been for years."

'The Democratic Spring'

Stacey Abrams won Georgia's Democratic gubernatorial primary in May. Jessica McGowan/Getty Images

Many Democrats and left-wing activists say a November blue wave won't happen without strong campaigns on the far left.

Katrina vanden Heuvel, the editor of the progressive magazine The Nation, last month called recent left-wing electoral successes part of a "Democratic Spring."

"Instead of bemoaning the moribund Democratic Party, progressives are increasingly moving to take it over," vanden Heuvel wrote in a Washington Post op-ed article. "If there is to be a blue wave, it will build from the enthusiasm of the Democratic base demanding change."

But others continue to advocate a Clinton-esque, centrist approach. Ferguson said the Democratic Party won the majority of American votes in 2016 for a reason and shouldn't stray too far from the mainstream if it wanted to maintain that majority.

But he's not surprised a socialist platform appeals to voters in New York's 14th District.

"If a Democrat in this district can't champion those policies, where can they?" he said.