A 28-YEAR-OLD political newcomer has won a landslide victory against a 10-term incumbent and senior Democratic Party figure, possibly signalling a US political shake-up.

Alexandria Ocasio-Cortez beat veteran politician Joe Crowley, 56, to his seat in the Democratic Party’s congressional primary in New York City, winning 57.5% of the vote.

Footage of the moment the progressive Bronx local realised she’d won shows her speechless with her hand over her mouth, supporters in tears behind her at the stunning victory.

Ms Ocasio-Cortez, a Latina woman of Puerto Rican descent, now faces off against Republican opponent Anthony Pappas in the November midterm elections for the district seat, which covers parts of the Bronx and Queens.

A former Bernie Sanders organiser, it’s her first time running for office.

If she wins, Ms Ocasio-Cortez will become the youngest woman ever elected to the US Congress.

The win by Ms Ocasio-Cortez, who was working as a bartender as recently as November 2017, is a shocking blow for Representative Crowley, who was a potential candidate for future leader of the House Democrats.

In an interview with CBS News the morning after her win, she described herself as an “unapologetic champion for economic, social and racial dignity in the United States.”

“Voters also knew that I was the only candidate in the race that did not take corporate money in a time when economic marginalisation is really increasing in New York City,” Ms Ocasio-Cortez added.

“So I think it created a lot of trust in our community and our message really inspired a lot of folks that don’t usually turn out in an off-year midterm primary.”

Ms Ocasio-Cortez’s campaign centred on providing Medicare for all, justice system reform, banning assault weapons and ending corporate influence in public elections.

Some analysts said the furore over US President Donald Trump’s immigration policy energised voters in the heavily Hispanic 14th Congressional District to go with the newcomer.

Last weekend, just days before the primary, Ocasio-Cortez left New York to join protests at an Immigration and Customs Enforcement detention centre in Texas.

Ms Ocasio-Cortez, a liberal activist with Puerto Rican roots, never wavered from her message that the Irish-American Mr Crowley was out of touch with his district and could no longer represent a community of Latino, Asian and African immigrants.

“For 20 years our rents have been going up, health care has been getting more expensive and our incomes are staying the same,” she said in the only debate she had with Mr Crowley, on NY1.

“Not all Democrats are the same and I am proud to be the only Democrat in this race that rejects all corporate money and champions and advances improved and expanded Medicare for all, a federal jobs guarantee, tuition-free public college and the abolition of [Immigration and Customs Enforcement].”

Her election follows several wins by Democratic women in primaries across the US.

Last month, Georgia’s Stacey Abrams won her seat, and will become America’s first African-American woman to serve as governor should she be elected in November.

In Kentucky, Marine combat pilot Amy McGrath comfortably won her seat against Lexington mayor Jim Gray.

Democratic Senator John Yarmuth from Kentucky may have summed it up best after Ocasio-Cortez’s win:

“One of my takeaways is that you don’t want to run against a Democratic woman this year.”