New Delhi, June 11 -- About 75,000 voters in a pocket of northwest England are about to make a momentous decision. They will cast ballots in a contest that may well pick the U.K.'s next prime minister, or plunge Britain's febrile politics into even more turmoil. Possibly both.

Some of them aren't too enthusiastic.

"I think they're all a waste of time," said Shirley Prior on the choice of candidates in Makerfield, where a special election on June 18 has drawn interest from journalists around the world. That level of attention is all-but unheard of for a midterm by-election to fill one of the 650 seats in the House of Commons.

If Andy Burnham from the center-left Labour Party wins, there's a strong chance he will replace embattled Prime ...