Millennial socialist candidate Alexandria Ocasio-Cortez has won the Democratic primary for the New York 14th Congressional district.
Ms Ocasio-Cortez, 28, defeated political veteran Joe Crowley, 56, on Tuesday night (local time).
Mr Crowley, who has not faced a challenger from his own party in 14 years, was thought to be a future party leader or Speaker of the House.
But Ms Ocasio-Cortez, a former Bernie Sanders volunteer from a Puerto Rican family, won with 57.5% of the vote.
The district won covers parts of the Bronx and Queens with a largely working-class population made up of 70 percent people of colour.
Ms Ocasio-Cortez supports universal healthcare, tuition-free university, and criminal justice reform.
She also wants to abolish US Immigrations and Customs Enforcement (ICE).
"We are committing human rights abuses on the border and separating children from their families and that is part of the structure of the agency," she told CNN.
"We can replace it with a humane agency that is directed towards safe passage instead of criminalisation."
She graduated from Boston University with a degree in economics and international relations. After graduating she worked as a waitress and bartender to supplement her mother's income as a cleaner and bus driver.
Ms Ocasio-Cortez will now face Republican candidate Anthony Pappas in the November mid-term election.
If she wins, she will become the youngest ever woman elected to Congress.
Ms Ocasio-Cortez's campaign was endorsed by Sex and the City star Cynthia Nixon who is running to be the next governor of New York City.
This comes alongside a wave of progressive women in politics, including New Zealand's own Jacinda Ardern being elected as the world's youngest ever female prime minister.