The political landscape of the Plurinational State of Bolivia shattered on Sunday when the centrist senator Rodrigo Paz Pereira scored a stunning first-place finish in presidential elections, setting up an October runoff against the right-wing former president Jorge “Tuto” Quiroga. Paz, who had been polling under 10 percent, captured 32.8 percent of the vote while the Movement for Socialism (MAS)—which has dominated Bolivian politics for two decades—suffered a catastrophic collapse.

The scale of MAS’s defeat defies easy explanation. The party that won 68 percent of the vote in La Paz department just five years ago managed barely 4 percent this time. Its official candidate, Eduardo del Castillo, finished sixth with just 3.2 percent nationally. The party’s founder, the former president Evo Morales, had called on supporters to cast null ballots after being barred from running, but even that can’t account for the magnitude of the collapse.

Paz’s victory represents more than a political upset; it’s a repudiation of two decades of economic populism during Bolivia’s worst economic crisis in a generation. The country faces nearly 25 percent annual inflation, critical shortages of dollars and fuel, and widespread protests over rocketing prices. MAS built its dominance during the commodities boom of the 2000s and early 2010s, when high global prices for Bolivia’s natural-gas and mineral exports funded social programs that delivered tangible improvements in living standards, particularly for indigenous and working-class people.

The puzzle is how a senator from a wine-producing region polling in single digits managed to topple a socialist movement that had governed for 20 years and captured 55 percent support nationally just five years earlier.

What happened?