U.K.’s Labour Fights to Keep Blue-Collar Voters From Moving to the Right

HECKMONDWIKE, England—For nearly a quarter of a century, Britain’s Labour Party could count on the support of blue-collar workers in this northern English town once famed for its textile industry.

Today, the party is fighting to win a crucial local election here following the resignation of a Labour parliamentarian who represented the district. A victory could help shore up support among working-class voters who have defected in much of the country to Prime Minister Boris Johnson’s Conservative Party.

But if—as opinion polls predict—the district of Batley and Spen does flip to the Conservatives in Thursday’s vote, it would be the latest brick in Labour’s once-formidable postindustrial voting base to crumble, further highlighting what has become a historic slump for the party.

Off a bustling main street in Heckmondwike lined with advertisements for Labour, Paul Curtlees recently watched workers file out of a factory after a day sewing curtains. Mr. Curtlees, a manager at a soft-furnishing supplier, says he switched from Labour to the Conservative Party two years ago.

On the shop floor, his colleagues are considering voting Conservative for the first time. “They have just got no faith in the Labour Party,” he says.