MIAMI — A year ago, when Venezuela’s government seemed to be on the brink of collapse, the Venezuelan diaspora in South Florida buzzed with energy, holding rallies and hosting prominent political leaders, including Vice President Mike Pence, who embraced its cause of ousting the nation’s leftist president, Nicolás Maduro.

As the months passed and Mr. Maduro remained in power, anticipation turned to resignation. Venezuelan-Americans saw interest in their country’s future fading, both from the headlines and from inside the White House.

So when Juan Guaidó, the opposition leader who has declared himself Venezuela’s interim president, appeared on Saturday in Miami, his supporters hoped to revive public interest in his efforts — and to perhaps once again attract the attention of President Trump.

Several thousand Venezuelans gathered for the event in a cavernous hall at the Miami Airport Convention Center. Traditional Venezuelan music played to the boisterous crowd, and many of the people were decked in the yellow, blue and red colors of the country’s flag.