Sarah Bruce does not consider herself to be apolitical, much less apathetic. The 28-year-old radio producer studied politics at university, cares passionately about environmental issues and maternity benefits, and voted in the U.K.'s general elections in 1997 (for Labour) and 2001 (for the Green Party). But now she doesn't respect any of the three major parties, and has no intention of going to a voting booth on May 5: "What's the point?"
Although their reasoning varies, millions of Britons will join Bruce this Thursday in not casting a ballot. A smaller and smaller percentage of Britons is taking...