He is an autocrat condemned inside and outside his country as having stolen the nation’s last election. Yet on Friday, Nicolás Maduro, the Venezuelan president who has overseen his country’s dramatic decline — including runaway inflation, blackouts, hunger, mass migration and the unraveling of the nation’s democracy — is set to be sworn in for a third term in office.

If he serves the full six years, it will extend his party’s reign into its third decade.

Mr. Maduro will return to Miraflores, the presidential palace in Caracas, even after millions of Venezuelans used the ballot box to express a desire for change. And he will do so amid his harshest crackdown yet, with the police and military in riot gear blanketing the streets of the capital; journalists, activists and community leaders in prison; and a broad expansion of his surveillance apparatus.

The man the United States and others say won the election, Edmundo González, remains in exile, forced to flee to Spain or face arrest, while the country’s most important opposition leader, María Corina Machado, has been in hiding inside Venezuela.

On Thursday she emerged for the first time since August, joining street protests against Mr. Maduro in Caracas, the capital. She stood atop a truck while thousands of supporters, all risking detention, shouted “freedom! freedom! freedom!”

Afterward, she was briefly detained by unidentified adversaries and then released.

There have been few other recent protests against the government, and the ever-present threat that security forces will imprison civilians is likely to make it difficult for Ms. Machado to continue to rally supporters to the streets.