Will Britain's Labour Party Prefer Corbyn to Winning?

Jeremy Corbyn's candidacy is about as improbable as his ideas. He didn't even ask to be on the ballot for leader of the U.K.'s Labour Party, yet he's ahead in the polls -- and part of his appeal is his unapologetically old-fashioned economic thinking.

Imagine Bernie Sanders winning the Democratic Party's nomination for president in the U.S. Like Sanders, Corbyn is a longtime activist and campaigner, guided by personal hard-left conviction rather than party loyalty or strategic calculation. For both men's supporters, that's the appeal -- and, for their parties, that's the danger.