David Crowley is projected to have won a primary election to become the Democrat's candidate for Wisconsin governor, in a surprise result that halts a winning streak for the party's left wing.

With almost all votes counted in the Midwestern state, Crowley, the more centrist candidate, has secured a narrow victory over Francesca Hong, according to a projection made early on Wednesday by the BBC's partner, CBS News.

Anti-establishment Democrats had previously recorded wins across the US that had rattled the party leadership in Washington. Many pundits expected Hong to continue that trend.

Crowley will now face off in November against Tom Tiffany, who easily won the equivalent Republican contest.

Crowley, the chief executive officer of the state's Milwaukee County, posted on X to say it was time to "get to work".

He reiterated that his missions were "making life more affordable, strengthening our schools, creating good-paying jobs, and making sure opportunity reaches every corner of our state".

Tiffany, meanwhile, currently serves as a US congressman and has the backing of US President Donald Trump.

He has also emphasised affordability issues, running on a platform that includes lowering taxes, supporting farmers and improving healthcare.

The state's political matchups are expected to be closely fought during November's midterm elections, which have also wider implications for the control of the US Congress.

The Hong-Crowley contest was just one of several that were held across the state and neighbouring Minnesota across Tuesday.

Meanwhile, in South Carolina, Darline Graham Nordone advanced to a run-off vote later this month in a special Republican primary for the US Senate which was held following the death of her brother, Senator Lindsey Graham.

She will face off against Democrat Annie Andrews to fill the vacant seat.