Many of those marching with Mr. Guaidó were older or retired Venezuelans. After six years of economic instability, millions of younger Venezuelans have fled the country, depriving the opposition of potential voters and protesters.

“It’s just the elderly here because our sons have already gone,” said María de Guevara, 70, as she held up a sign that read, “I refuse to give up. Liberty!”

The march set off from an opposition stronghold in eastern Caracas toward the National Assembly downtown, where the government staged a parallel rally.

While Mr. Guaidó’s call on Tuesday drew more people than the last few protests, it was a far cry from the hundreds of thousands who came out to support him a year ago, when he accused Mr. Maduro of electoral fraud and declared himself the country’s interim president.