CARACAS, Venezuela — Thousands of people marching in support of the Venezuelan opposition on Tuesday were met with tear gas from security forces as they tried to rekindle the struggle to oust President Nicolás Maduro, a movement that has flagged amid repression, an economic crisis and fatigue.
It was the first protest called by the opposition leader Juan Guaidó since he returned from an international tour this year in which he met with dozens of world leaders, including President Trump, and won assurances of additional American sanctions against Mr. Maduro’s government. At home, however, Mr. Guaidó’s movement has struggled to maintain momentum after a year of protests, drawing ever-smaller crowds.
To deter protesters on Tuesday, the government suddenly announced military exercises in the capital and surrounded the National Assembly with tanks. Rows of police officers dispersed protesters with tear gas when they tried to enter central Caracas.
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 a protester, 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 of supporters 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.
As time went on and the protests shrank, they became more about merely showing signs of political life.
Without a major breakthrough, Mr. Guaidó risks being replaced by another leader as the standard-bearer of the opposition, according to Michael McCarthy, a Washington-based Venezuela analyst. “While Guaidó can reliably count on United States economic pressure on Maduro to continue, he cannot reliably count on popular pressure from the broader population,” Mr. McCarthy wrote in a client newsletter on Tuesday.
After the outpouring of protests a year ago, the government has steadily choked off Mr. Guaidó’s ability to organize people. Intelligence agents have detained more than a dozen of Mr. Guaidó’s allies, and armed government gangs, known as colectivos, regularly break up protests.
In January, security forces blocked opposition lawmakers from entering the National Assembly, where they hold the majority of seats, depriving Mr. Guaidó of symbolic control of Venezuela’s last democratically elected institution. The assembly has effectively ceased to function.
Despite a firm grip on the streets, Mr. Maduro is facing his own problems. The collapse of global oil prices this week threatens to devastate Venezuela’s already shrinking oil exports, which remain the most important source of state revenues.
Mr. Maduro has partially bypassed sanctions by bartering crude oil for essential goods such as food and gasoline, a scheme that will likely be undermined by market turmoil and tightening American sanctions.