It was a rare diplomatic gamble when the three leaders of Latin America’s largest democracies inserted themselves into the high-stakes standoff between Venezuela’s Nicolas Maduro and his opponents over who won the country’s presidential election. The presidents of Brazil, Colombia and Mexico broke from decades of hands-off diplomacy toward Venezuela and their own reluctance to meddle in a neighbor’s sovereign affairs. But some experts say the peacemaking effort is losing steam before barely getting off the ground. They cite misgivings by Mexico’s outgoing president and divisions among Latin America’s left. The main outcome so far, they say, has been to grant Maduro precious time to consolidate his rule and jail opponents since the July 28 vote.