Sun Valley residents vote at the polling station located at Our Lady of The Holy Church on election day at the Sun Valley's Latino district, Los Angeles County, on November 6, 2012 in California.AFP PHOTO /JOE KLAMAR (Photo credit should read JOE KLAMAR/AFP/Getty Images)

Washington (CNN)The out-of-nowhere upset of Democratic Rep. Joe Crowley in Tuesday’s New York primary has stunned the Democratic establishment and shook up the party’s likely line of succession to become the next House speaker.

Crowley was ousted from his Queens district by Democratic socialist Alexandria Ocasio-Cortez, a 28-year-old Latina running her first political campaign. She is now likely to be the youngest woman ever elected to the House.

It was the most shocking result of 2018’s political season so far, and — though Democrats have avoided intra-party feuds so far this year — could signal a restive base as the 2020 presidential primary approaches.

A 28-year-old Democratic Socialist just ousted a powerful, 10-term congressman in New York
A 28-year-old Democratic Socialist just ousted a powerful, 10-term congressman in New York

Crowley, the No. 4-ranking House Democrat, was widely seen as the likely successor to House Democratic leader Nancy Pelosi. And because Pelosi is likely to have a hard time getting 218 votes to become speaker if Democrats win a narrow majority in November, that could have positioned Crowley to take the speakership against Rep. Steny Hoyer, now the House minority whip.

Two Democrats said the next speaker’s job is more unpredictable than ever — and Hoyer’s path to become speaker is far from clear. One Democrat said the jockeying will begin immediately.

“It’s clearly a signal that people want to get rid of the old and put in the new,” one Democratic House member told CNN.

Until now, there had been few signs of a mounting progressive insurgency. Kara Eastman had defeated former Rep. Brad Ashford in a Nebraska Democratic congressional primary and Democratic socialists had won down-ballot races in Pennsylvania and elsewhere. But progressives declined to challenge the party’s sitting senators, and in the most important election of 2017 — the Virginia governor’s race — Lt. Gov. Ralph Northam defeated his more liberal primary opponent, former Rep. Tom Perriello. Now, Ocasio-Cortez’s victory could embolden liberal challengers in both 2018 and 2020.

Crowley quickly conceded and backed Ocasio-Cortez, who said in her victory speech that “what we proved tonight is that sometimes the deep midnight and darkness that it feels in our political environment, that there is still hope for this nation.”

President Donald Trump, meanwhile, trolled Crowley, suggesting on Twitter — wrongly, given the overwhelmingly…