MSNBC's Kornacki on millennial challenger beating Crowley: 'This is a seismic political upset!'

MSNBC's Steve Kornacki called the upset victory by 28-year-old Alexandria Ocasio-Cortez, a former organizer for Sen. Bernie SandersBernard (Bernie) SandersSenate to vote Monday on Trump's VA nominee Senate approves resolution warning Trump not to hand over US officials GOP leader blocks resolution backing intelligence community on Russia MORE’s (I-Vt.) presidential campaign, in New York's 14th Congressional District a "seismic political upset."

“We saw these numbers coming in, we couldn’t believe it. We checked, we reloaded. This is a seismic political upset!” said Kornacki, who serves as a national political correspondent for NBC News and MSNBC, during the network's coverage of primary races late Tuesday

Ocasio-Cortez beat 10-term incumbent Rep. Joseph Crowley (D-N.Y.) easily, gaining 57.5 percent of the vote compared to his 42.5 percent.

“To put this in some perspective,” Kornacki added, “Joe CrowleyJoseph (Joe) CrowleyPoll: Cuomo expands lead over Nixon in New York Dem primary Election Countdown: Senate, House Dems build cash advantage | 2020 Dems slam Trump over Putin presser | Trump has M in war chest | Republican blasts parents for donating to rival | Ocasio-Cortez, Sanders to campaign in Kansas Crowley tweets: 'Still not running' MORE has been there since 1998, he was thought to be the next Democratic leader in waiting, potentially a Speaker of the House here, he runs the Queens County Democratic Party in the old sense of the word.”

Ocasio-Cortez's victory in the district, which covers parts of New York boroughs Queens and the Bronx, sent shockwaves through the political world, with the former bartender being the top-trending topic on Twitter Wednesday morning.

"This photo is from Nov. 14, 2017. Alexandria Ocasio-Cortez, 28, was then working as a bartender. Less than a year later, she defeated the likely next Speaker of the House, and will almost certainly be the youngest woman ever elected to Congress," wrote Washington Post reporter Jeff Stein.

Ocasio-Cortez won despite Crowley outspending her nearly 10-to-1, with the incumbent spending $1.09 million to her $127,000.

Sanders took to Twitter to congratulate her, calling the victory "extraordinary."