Jair Bolsonaro, the former Brazilian president charged with trying to cling to power after losing the country’s last election, is poised to stand trial starting Tuesday.

Prosecutors argue Mr. Bolsonaro, 70, oversaw a vast plot to overturn the 2022 election that sought to sow unfounded doubts about the results; hand the military special powers; dismantle courts; and even poison his rival, Luiz Inácio Lula da Silva, who narrowly beat him at the polls.

For many in Brazil, which emerged from a brutal military dictatorship just four decades ago, a successful prosecution of Mr. Bolsonaro would represent a victory for democracy.

But the way Brazil is attempting to reach that victory — through an extraordinarily empowered Supreme Court — has also left the country grappling with uncomfortable questions over the very democracy it sought to protect.

And to Mr. Bolsonaro and his supporters, the charges against him amount to political persecution, aimed at thwarting his political comeback in next year’s presidential election. Mr. Bolsonaro says that he explored only legal means to remain in office after losing an election he claims was stolen from him. (There is no evidence of fraud.)

Mr. Bolsonaro’s case has also triggered a diplomatic crisis between the Western Hemisphere’s two largest nations, as President Trump has used tariffs and sanctions to try to force Brazil’s judiciary to drop the charges against its former leader, who is also a political ally of Mr. Trump.