Jack Nicas for the NYT:

For the past 10 weeks, supporters of the ousted far-right President Jair Bolsonaro had camped outside Brazilian Army headquarters, demanding that the military overturn October’s presidential election. And for the past 10 weeks, the protesters faced little resistance from the government.

Then, on Sunday, many of the camp’s inhabitants left their tents in Brasília, the nation’s capital, drove a few miles away and, joining hundreds of other protesters, stormed Congress, the Supreme Court and the presidential offices.

By Monday morning, the authorities were sweeping through the encampment. They dismantled tents, tore down banners and detained 1,200 of the protesters, ferrying them away in buses for questioning….

Whatever security lapses may have occurred, Sunday’s riot laid bare in shocking fashion the central challenge facing Brazil’s democracy. Unlike other attempts to topple governments across Latin America’s history, the attacks on Sunday were not ordered by a single strongman ruler or a military bent on seizing power, but rather were fueled by a more insidious, deeply rooted threat: mass delusion.

Millions of Brazilians appear to be convinced that October’s presidential election was rigged against Mr. Bolsonaro, despite audits and analyses by experts finding nothing of the sort. Those beliefs are in part the product of years of conspiracy theories, misleading statements and explicit falsehoods spread by Mr. Bolsonaro and his allies claiming Brazil’s fully electronic voting systems are rife with fraud.

Mr. Bolsonaro’s supporters have been repeating the claims for months, and then built on them with new conspiracy theories passed along in group chats on WhatsApp and Telegram, many focused on the idea that the electronic voting machines’ software was manipulated to steal the election. On Sunday, protesters stood on the roof of Congress with a banner that made a single demand: “We want the source code.”