In Hartlepool, a tough, proud English port town whipped by bitter North Sea winds, people have long felt ignored by politicians in far-off London. Political parties in Britain’s Brexit-dominated December election are battling fiercely to win Hartlepool and places like it: working-class former industrial towns with voters who could hold the key to the prime minister’s office at 10 Downing Street. Hartlepool has elected lawmakers from the left-of-center Labour Party for more than half a century.