Call for canvassers prompted Trump to allege ‘foreign interference’ – but practice has been going on for a long time

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It is usually just a week, but sometimes longer. The hours are long, the socialising limited, and there is no reward beyond free accommodation in a shared house, recalls one Labour staffer who spent three weeks knocking doors and ferrying campaign material for the 2008 campaign to put Barack Obama, then a junior senator from Illinois, in the White House.

What volunteering in a US election does offer is a walk-on part in a moment in history.