On the surface, things seem calm. An outsider walking through the streets would not get the impression that a presidential election is about to be held. Looking out the window, I notice that the Brazilian flags — which have come to represent support for Mr. Bolsonaro — have been removed from the neighboring facades. An ambiguous sign: It could be a pre-emptive response to defeat, or the calm before the storm. There’s not even much talk among friends and family concerning the election; the lines were drawn in 2018 and have not moved much since then.

Yet for all the social polarization, there is still enormous support for democracy here: 75 percent of citizens think it is better than any other form of government. Right from the beginning, Mr. da Silva has been trying to exploit that common feeling and open up a broad front against Mr. Bolsonaro. He picked a former adversary from the center-right, Geraldo Alckmin, as his running mate; assiduously courted business leaders; and secured endorsements from prominent centrists. In this comradely atmosphere, supporters of the center-left candidate, Ciro Gomes, currently about 6 percent in polls, may even throw their votes behind the former president. If that happens, Mr. Bolsonaro will surely be beaten.

That glorious prospect does little to dispel the anxiety enveloping the country. It’s physically impossible not to dwell on what might happen. The possibilities are terrifying: The polls might be wrong, and Mr. Bolsonaro could win. The polls might be right, and Mr. Bolsonaro could refuse to concede defeat, and even initiate a coup. Each day now seems to be the length of a day on Venus — around 5,832 hours — to go by the agitation of my Twitter feed.

There’s simply too much at stake. For one, there’s the democratic process itself, which has been put through the wringer by Mr. Bolsonaro. For another, there’s the future of our judiciary. Just next year, there will be two vacant seats on the Supreme Court, out of a total of 11 seats. If in power, Mr. Bolsonaro would surely seize the chance to make pick hard-right justices as he did with his last two appointees. A Trump-style remaking of the judiciary could be coming down the line.

Then there’s the environment. So far this year, more forest fires have been recorded in the Brazilian Amazon than in all of 2021, which was already catastrophic enough. Since the start of September, dense plumes of smoke have covered several Brazilian states. Under Mr. Bolsonaro’s administration, deforestation has increased, environmental agencies have been dismantled and Indigenous deaths have risen. Reversing these disastrous environmental policies could not be more urgent.