WASHINGTON — Cori Bush, a nurse and Black Lives Matter activist, is all set to become the first black woman to represent Missouri in US Congress as she ousted a 10-term political veteran in Missouri's Democratic primary election.

Bush’s primary win essentially guarantees her a seat in Congress representing the heavily Democratic St. Louis area.

Bush, who was once homeless woman, beat Congressman William Lacy Clay by a margin of three percent. The seat has been held by either Clay or his father, a civil rights activist, since the 1960s.

Her victory is the latest upset against establishment Democrats by newcomers.

She had campaigned for Senator Bernie Sanders during his presidential run.

Praising her on Twitter, Sanders said Bush would "take on the corporate elite of this country when she gets to Congress".

“Congratulations to @CoriBush on her primary victory tonight! She is a true progressive who stands with working people and will take on the corporate elite of this country when she gets to Congress,” Sanders said in his tweet.

Bush, 44, had lost to Clay, 64, during the 2018 primary in Missouri.

Clay is a longtime congressman who has represented the St Louis area for two decades. His father is a co-founder of the Congressional Black Caucus.

Clay campaigned on his congressional record while highlighting Bush's lack of political experience. — Agencies