Former South Carolina Governor Nikki Haley won her first contest in the Republican presidential nomination race in Washington D.C. on Sunday.

Her triumph in the D.C. primary breaks rival Donald Trump's sweep of the Republican presidential voting contests.

In the US electoral system, voters head to the polls for either primaries or caucuses depending on the state they live, to elect a candidate for the presidential election. The presidential nominees are then declared during conventions held later in the year.

The general election takes place on November 5. 

Haley wins D.C. ahead of Super Tuesday

The former United Nations ambassador has pledged to stay in the race at least through Super Tuesday this week, when 15 states and one US territory will vote. Trump has a commanding lead according to opinion polls in nearly all of those states.

Trump won the most delegates in the eight early-voting states in January and February and is poised to rack up more delegates on Super Tuesday.

To win the Republican nomination for the presidential election ballot in November, a candidate needs to secure at least 1,215 delegates.

In Washington D.C., Haley won 62.9% of the vote, while Trump garnered 33.2%. Because Haley won more than half of the votes, she won all 19 delegates that were up for grabs, but is still a long way off winning the party's nomination.

Republicans in Washington reject Trump

"It’s not surprising that Republicans closest to Washington dysfunction are rejecting Donald Trump and all his chaos," Haley campaign spokesperson Olivia Perez-Cubas said in a statement. Haley was the first woman to win a Republican primary in US history, her campaign said.

Washington is one of the most heavily Democratic jurisdictions in the nation, with only about 23,000 registered Republicans in the city.

The capital's moderate set of Republicans, many of whom work in politics, are vastly different from those in other states. They believed that Washington could represent Haley's best chance to win a primary.

Trump's campaign issued a statement shortly after Haley's victory sarcastically congratulating her on being named "Queen of the Swamp by the lobbyists and D.C. insiders that want to protect the failed status quo."

Though Haley faces near-impossible odds in her quest to win the Republican nomination, her win will likely inoculate her from criticisms that she is not able to win a single primary.

Some Republicans, however, will see her popularity in Washington as a negative. Many party leaders, including Trump, portray the city as one that is run by elites out of touch with their voters.

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rm/wd (AP, Reuters)