Labour’s summer leadership election has entered its final month; ballot papers go out to members and registered supporters from August 14th. The latest polling by YouGov suggests that—even under the party’s fiddly, multi-stage electoral system—the far-left candidate, Jeremy Corbyn, is on track to win. Where is his support coming from? Party members, after all, voted for the moderate David Miliband in 2010 (over his more left-wing brother, Ed, who won thanks to union votes). The poll sheds some light on the mystery: although the party’s membership as a whole supports Mr Corbyn, different generations vary starkly. Those who joined before Mr Miliband became leader would back Yvette Cooper, a relative centrist. Those who signed up under his leadership prefer Mr Corbyn; those who have arrived since the election on May 7th even more so. In other words, the Labour Party is tilting to the left. That should worry moderate MPs, who are already plotting to overthrow their hard-left comrade if he wins on September 12th. They can oust him fairly easily. Less so the membership that elected him.