The public relations high-flyer is the man who drove the election campaigns for both Argentina's Carlos Menem and Brazil's Luiz Inacio Lula da Silva to the presidency of their respective countries.
It is hard to imagine such political opposites but this holds no problem for Mendonca.
Now he is trying to win the key sate of Sao Paulo for Brazil's governing Workers' party as the campaign begins in earnest for November's elections.
For some he is no magician, just someone who capitalises on the power of television in Latin America where illiteracy rates are high.
"I don't think he is singularly a big person," says Fabio Wanderley Reis, professor of politics at Minas Gerais University.
"He is a specialist at marketing and publicity. He is showing a professional character. It's not about ideologies. He is good in campaigns but he is not irreplaceable. He could be substituted by anyone."
The president clearly has another view. Having lost three elections, Lula, the story goes, said that he would run one more time only if the Workers' party used Mendonca.
His slick makeover worked, and Lula was transformed from a gruff-voiced, T-shirt and denim man-of-the-people to a suit-and-tie pragmatist with straightened teeth.
Promotional materials has likened
President Lula to Kofi Annan
When the government lurched into a crisis over backhanders from an illegal gambling scandal in March, it was Mendonca who emerged with an extra US$2.5 million to spend convincing the public that Lula was still on the right track.
After more than 500 days in power, Mendonca's latest efforts have been to associate Lula with UN Secretary-General Kofi Annan in political TV slots. Annan was in Sao Paulo this month for the four-yearly United Nations conference on trade and development.
Brazilian troops have been stationed in Haiti leading the international peacekeeping force as Lula tries to wake Brazil from its traditional slumber in world affairs.
Ironically, in the forthcoming mid-term elections, Mendonca will be warring against a political candidate whose own remarkable makeover first brought the advertising king to note.
Paulo Maluf was a serving mayor during the military junta, but Mendonca gave him an overhaul with a successful TV campaign that focused on the public works that had been created during his tenure. "Maluf made it" was the slogan. Maluf duly became mayor of Sao Paulo in 1993.
Former Argentine president
Carlos Menem with his family
Today Maluf is running his re-election campaign under investigation over allegedly salting away hundreds of millions of dollars in offshore bank accounts during his four-year term. How he could do with Mendonca now, who instead is chief propagandist for his rival and the current mayor Marta Suplicy.
Despite his apparent influence, Mendonca appears to raise the hackles of political scientists.
"I've got nothing to say about Duda Mendonca," says Carlos Novaes, president of the research institute Datanexus. "He is not worth talking about."
When the then-incumbent Argentine president, Carlos Menem, saw Mendonca's work with Maluf he brought the Brazilian in to run his battle for a second term, using the same slogan in Argentina that had been used in Sao Paulo - "Menem made it." Menem won a second term.
Now his shamed former client is holed up in Chile evading two extradition warrants put out by the Argentine foreign ministry over embezzlement.
When he was first named special consultant by the communications minister Luis Gushkin, Mendonca was forthright on those who attacked his profession.
"Who is talking the truth? The publicity and the marketing or the press controlled by half a dozen families in Brazil?" he asked.
Duda Mendonca and Associates received $33 million to spend this year in a contract from the presidency of the republic.
His work will be vital. The mid-term elections are seen as a crucial test for the Workers' party which is governing for the first time. This week it was revealed that President Lula's support had slid even further to his lowest rating since taking office - just 29% support of the electorate.
Duda Mendonca's 2002 book was
titled Cases and Things
Currently the Workers' party candidate, Suplicy, is neck-and-neck with Jose Serra, the man Lula defeated to become president in 2002. Maluf is still a close third.
Interestingly, Mendonca has relied on his past successes for his new campaign slogan for Suplicy. After "Maluf made it" and "Menem made it" he has come up with ... "Marta made it well".
Mendonca was recently in Cannes for the annual advertising industry's version of the film festival.
A past prizewinner, Mendonca was due to bring out a film of the 2002 elections propaganda, a How-I-won-the-election-for-Lula film, but there has been no release date set.
Perhaps the publicity maestro is waiting for an upturn in the president's fortunes. He clearly wants to be associated only with success.