It was showtime. Bounding into the ballroom, Trudeau was greeted by hundreds of clapping Windsorites. He took the podium in front of a giant, freshly steamed Canadian flag that travels in its own suitcase. “I’m here tonight because Windsor matters,” he said. People cheered. “It’s about time we had a government in Ottawa that understood that.”

The government in Ottawa is, of course, that of Prime Minister Stephen Harper. During his nine years in power, Harper, a Conservative from Alberta, has managed to nudge politics well to the right of center, at least by Canadian standards. He has lowered corporate and sales taxes, kept the country out of international climate agreements, and toughened criminal sentences.

Harper is due to face voters on or before October 19, in what is likely to be his toughest fight yet. In part, that is because his leading opponent is the son of the man who—according to a survey conducted by Harper’s own government—is widely considered the most inspiring Canadian of all time: Pierre Elliott Trudeau. The elder Trudeau served as prime minister almost continuously from 1968 to 1984, keeping the country together in the face of a separatist movement in Quebec, distancing Canada from the foreign policies of Richard Nixon and Ronald Reagan, and, in 1982, formally liberating the Canadian constitution from British control. He was cerebral—educated at Harvard, Sciences Po, and the London School of Economics, he sometimes annotated documents in Latin—yet dashing and spontaneous. Photographers caught him sliding down a banister, and performing a pirouette behind Queen Elizabeth’s back. He dated Barbra Streisand at one point. He was known to wear a cape.

The year before he became prime minister, Pierre met Margaret Sinclair, a self-described flower child 29 years his junior, at a Club Med in Tahiti. She was vacationing with her parents; he was there to read Edward Gibbon and contemplate his political future. They married in March 1971, and Justin was born that Christmas, followed by two more boys, Alexandre and Michel. But by 1977, the marriage had soured, and Margaret ran away to party with the Rolling Stones, dance at Studio 54, and have a tryst with Ted Kennedy. (She would later reveal that her unhappiness and impulsiveness had stemmed partly from bipolar disorder.) As for Pierre, he moved on to other women, including the actresses Kim Cattrall and Margot Kidder.

Justin and his brothers were the first children to live at 24 Sussex Drive, Canada’s prime-ministerial residence. He recalls a boyhood of canoe outings near the prime minister’s summer residence and flights to foreign capitals, all under the watch of a Royal Canadian Mounted Police security detail. Before he turned 14, he had met Margaret Thatcher, Ronald Reagan, and Helmut Schmidt, and attended Leonid Brezhnev’s funeral. He remembers Princess Diana stopping by 24 Sussex for a swim.