Juan Guaido "tried everything" in 2019 to force Venezuela President Nicolas Maduro from power, to no avail. Yet the 36-year-old opposition leader has vowed to re-launch the offensive this year.

The National Assembly speaker is set to be re-elected to his position on Sunday, but it is the top job currently occupied by socialist leader Maduro that he's after.

Just under a year since declaring himself acting president -- in a move recognized by the United States and more than 50 other countries -- Guaido pledges to "resist and insist."

His power struggle began brightly when Guaido showed ingenuity and skill in rallying supporters to protest and defying Maduro's authority in a number of ways -- including flouting a travel ban.

But his challenge petered out over the second half of 2019, though he's never given up his demand for the "usurper" Maduro to resign so a transitional government can take over ahead of new elections.

Guaido, like many in the international community, considers the leader's 2018 re-election to have been fraudulent.

"Juan is ready to take on the challenge, there's no doubt about that," lawmaker Olivia Lozano, a member of Guaido's Popular Will party, told AFP.

"I'm a survivor, not a victim," Guaido has said, recalling how he survived one of Venezuela's worst natural disasters as a teenager: the Vargas tragedy of December 1999, when mudslides caused by torrential rain killed thousands of people.

Back then, Guaido lived with his mother and five siblings in the coastal state of Vargas.

"I know what it means to be hungry," he said.

Hunger is something millions in his country are intimately familiar with now. Venezuela's economy has crumbled, with shortage of cash, food, medicine and other basics that have led millions to flee.

Guaido's survival instincts are sure to be tested this year with parliamentary elections due.

Maduro has vowed to leave Guaido and his supporters "sidelined."

The National Assembly is the only branch of government in opposition hands and Guaido can ill afford to lose it, despite the fact its every decision since 2017 has been annulled by the Supreme Court, which is loyal to Maduro.

Guaido, though, "is able to handle himself in crisis situations," said fellow opposition lawmaker Delsa Solorzano.

In a country used to authoritarian leaders with big personalities, Guaido is not a natural.

He's never been a great public speaker but he made history a year ago when he became the youngest person ever to preside over the legislature.

His prolific use of social media has certainly helped. He has 4.4 million followers on Instagram and another 2.3 million on Twitter.

Juan Guaido was a virtual unknown before rising to the National Assembly presidency and challenging Venezuela's President Nicolas Maduro
Juan Guaido was a virtual unknown before rising to the National Assembly presidency and challenging Venezuela's President Nicolas Maduro AFP / Federico PARRA

And he's proven a talented coalition-builder -- something Venezuela's divided and disorganized opposition badly needed, particularly with a number of its previous leaders either jailed or exiled.

Maduro, the hand-picked successor to late leftist firebrand Hugo Chavez, has dismissed Guaido as "a kid playing at politics."

Guaido remains unwavering in his promise to end 20 years of Chavism and solve Venezuela's economic crisis.

He may not have succeeded in his primary objective in 2019 but he'll get "a second chance," according to Benigno Alarcon, the director of political and government studies at the Andres Bello Catholic University in Caracas.

However, Guaido will have to "change strategy in a more realistic way."

His main failure was in trying to drive a wedge between Maduro and the armed forces, whose support has been crucial to keeping him in power.

Maduro can also count on support from China, Russia and Cuba.

Guaido has seen his popularity fall dramatically, from 63 percent at its height to just 39 percent in December, according to a poll by Datanalisis.

Recent accusations of corruption among his inner circle have been damaging, but he remains "the most popular political figure in Venezuela," according to Michael Shifter, president of the Inter-American Dialogue in Washington.

A virtual unknown before his dramatic self-appointment on January 23 last year, Guaido has had to absorb some blows.

He failed in a bid to bring in humanitarian aid in February that he hoped would demonstrate his ability to meet the people's needs amongst shortages of food and medicines.

And an attempted uprising in April fizzled out quickly as it didn't attract much support from members of the armed forces.

Peace talks mediated by Norway also failed to produce any advancement in Guaido's cause.

An industrial engineer by training, the Catholic father of a two-year-old says he's "tried everything."

Washington has sanctioned senior regime figures but Shifter warns Guaido also faces the possibility of losing US President Donald Trump's support.

"Trump has seemingly lost some interest in Venezuela since last January. He was led to believe that Maduro's fall was imminent," said Shifter.