George McGovern’s death Sunday marked the departure of a remarkably influential figure in American national politics. Though remembered largely for his landslide defeat to Richard M. Nixon in the 1972 presidential race, McGovern succeeded in reshaping the U.S. political landscape for the next 40 years.

His losing campaign forged the modern political party. Just as Barry M. Goldwater’s crushing defeat in 1964 mobilized a generation of conservative activists and transformed the GOP, McGovern’s insurgency led to the modern Democratic Party of Bill Clinton and Barack Obama. For the South Dakotan senator bequeathed to his party a reconstituted style of politics, a cadre of activists and an new path to electoral victory.

McGovern’s star-crossed campaign opened up the entire U.S. political process—he appointed, for example, the first national party chairwoman. More important though, he created a template for challenging the party establishment, one emulated frequently over the next 40 years — by the Republican right as well as the Democratic left.

Amid the collapse of the New Deal coalition, the alliance of liberals, labor, African-Americans and working class white ethnics around economic issues that had fueled Democratic politics through the 1960s, McGovern concocted the formula that his Democratic successors would use to reach the White House. He moved the presidential nominating process out of the smoke-filled room and into the primary election. McGovern’s campaign organized slates of activists, rather than cigar-chomping pols, as delegates to the Democratic National Convention; it energized true believers rather than political regulars more interested in patronage than ideology.

McGovern’s unlikely path to presidential politics began in 1968, as the public watched the Democratic Party tear itself apart on national television. Thousands of anti-Vietnam War demonstrators filled Chicago’s streets and parks and the city’s fabled political boss, Mayor Richard J. Daley had girded for action — assembling 12,000 Chicago police, 6,000 armed National Guardsmen, 6,000 U.S. Army troops and 1,000 undercover intelligence agents. They clashed with protestors for an entire week, while delegates in the Convention Hall traded insults and catcalls.