(Bloomberg) -- Keir Starmer’s poll-leading UK Labour Party took another parliamentary seat from Rishi Sunak’s governing Conservatives, overturning a significant majority and denting the prime minister’s hopes of wrestling back momentum ahead of a nationwide vote expected in the second half of the year.

Labour’s Damien Egan won 11,176 votes, a 44.9% share, in the special election in Kingswood, outside the southwest city of Bristol. Conservative Sam Bromiley got 8,675 votes. Reform UK’s Rupert Lowe came third, the Green Party’s Lorraine Francis followed and Andrew Brown finished fifth for the Liberal Democrats.

Though Labour has held a commanding lead over the Tories in surveys for over a year, the victory will still provide a boost given Starmer’s party has endured negative headlines in recent weeks. A U-turn on its flagship economic policy and a row over Labour’s candidate in another by-election threatened to undermine the narrative it’s heading for power for the first time in 14 years.

Yet Kingswood will add to evidence voters are turning away from the Tories and will likely embolden Sunak’s internal critics — not least because his party held Kingswood by more than 11,000 votes at the last general election in 2019.

A separate by-election in Wellingborough, central England, was also held on Thursday with votes set to be announced early Friday.

Read more: Sunak Faces Electoral Tests That Risk Encouraging Tory Plotters

The Kingswood by-election was triggered when former Conservative energy minister Chris Skidmore quit in protest over Sunak’s watering-down of the UK’s climate policy. He had been MP since 2010, though the district traditionally moved between Labour and the Conservatives since it was created in 1974.

Egan faces a short spell as Kingswood’s Member of Parliament because the seat will be abolished at the general election under boundary changes to reflect shifting demographics. Still, Labour made a strong push there because strategists saw it as a precursor to trying to oust Tory Jacob Rees-Mogg in neighboring North East Somerset at the UK vote.

Meanwhile, Sunak’s Tory opponents will be analyzing Reform UK’s performance, over fears that a split in the right-wing vote will facilitate a landslide Labour victory if repeated nationwide.

--With assistance from Rebecca Choong Wilkins.

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