BOGOTÁ, Colombia — When the leader of Venezuela’s opposition landed in Caracas this week following a world tour meant to drum up support for regime change, his country’s authoritarian ruler handed him neither an arrest, which would have galvanized supporters, nor the chance for a hero’s welcome at the airport.

Instead, President Nicolás Maduro appeared to greet his rival, Juan Guaidó, with the same policy of slow strangulation that has drained the opposition of much of its momentum over the past year, cracking down on his movement enough to wear down its members, but without going so far as to spur the world to action.

Moments before Mr. Guaidó arrived, Mr. Maduro’s supporters attacked journalists who were there to cover his arrival, punching them and dragging at least one woman by the hair. Once Mr. Guaidó landed, government backers chased him out of the airport, cutting off any plans he had to make a speech, and then attacked his car with traffic cones and at least one metal pole.

And as Mr. Guaidó slipped through, authorities arrested his uncle, accusing him, without presenting evidence, of bringing explosives into the country.