KEN MARTIN, the chairman of the Democratic-Farmer-Labour Party (DFL), Minnesota’s affiliate of the Democratic Party, tells a story about how the state’s governor, Tim Walz, got his start in politics. In 2004 Mr Walz was a high-school teacher in Mankato, a town of 45,000 people in the south of the state. In that year’s presidential election, he decided to take his class to a George W. Bush event. Unbeknown to him, his students had hatched a plan to tease the then president. “They all had [John] Kerry shirts on,” says Mr Martin. “They ripped their sweaters off and, well, they got kicked out of that rally by the Secret Service.” Mr Walz, according to Mr Martin, “was really pissed”—not at his students, but at the Bush campaign. “He called me up…he wanted to get involved,” says Mr Martin, who made him a local campaign organiser.