No major figure from the military had come out to support him — and many of the top brass said there were against his latest move.

“They are cowards!!” Defense Minister Vladimir Padrino López wrote on Twitter of the opposition. “We will stand firm in the defense of the constitutional order.”

“We will keep the peace,” was the message on the Twitter account of the military unit that controls Caracas. “Always loyal, traitors never!”

While Mr. Guaidó said that he had the support of many top commanders in the armed forces — even promising a list of their names — no wave of top officials had yet voiced their support publicly. He also appeared to lack the support of other bases in Caracas or other parts of the country, which remained quiet.

But photos and video from the streets of Caracas showed a few heavily armed men in uniform wearing the blue bands that represent an allegiance to Mr. Guaidó. Some of the armed men were pointing weapons from an overpass, with boxes of ammunition nearby. Others were seen amid the antigovernment protesters.

“I think enough time has passed that all the relevant actors have looked around and see that the power dynamic remains largely unchanged, that Maduro does not have democratic legitimacy but he still has de facto power,” said Geoff Ramsey, a Venezuela analyst at the Washington Office on Latin America.

“I think ultimately what we’re going to see coming out of this is both the government and the opposition recognizing that their hands were not as strong as they were,” he said.