Throughout the quake-ravaged capital, not far from the teeming slums and public plazas-turned-homeless encampments, newly erected green and white welcome home banners read: “Our mother is here already, our father is coming. We all agree.’’The “father” refers to the pending arrival of former President Jean-Bertrand Aristide, who is expected to return from South Africa on Friday — or as early as Thursday — despite diplomatic attempts to keep him away until after Sunday’s critical presidential and legislative runoff elections.

The fluttering green and white banners — in which the word “mother” refers to presidential candidate Mirlande Manigat — shows to what extent candidates in Haiti’s historic elections are willing to go to court Aristide’s supporters, but also how relevant he remains even after seven years in exile.

“The fact that the international community fears that the mere presence of Aristide could destabilize the whole game of cards shows that it has little confidence in the solidity of Haiti’s political system,’’ said Robert Fatton, a Haiti expert at the University of Virginia. “However, I would be more anxious about the post-electoral period than the elections themselves.’’

In separate telephone calls Tuesday, President Barack Obama and United Nations Secretary General Ban Ki-moon unsuccessfully tried to persuade South African President Jacob Zuma to delay Aristide’s return, sources told The Miami Herald.

Zuma replied he was under pressure by Aristide, who in January announced he was ready to return to Haiti at anytime. Zuma’s government then told Haitian officials to expect Aristide on Friday.

On Wednesday, South African’s Caribbean representative Mathu Joyini arrived in Port-au-Prince as part of the welcoming committee that is expected to include supporters from Miami and members of the Congressional Black Caucus. Also arriving was Aristide’s longtime eye specialist who flew from Miami, presumably to see his former patient who said that he needs to leave South Africa for medical reasons because he was “six years in eye surgery six times.’’

Now, as an anxious nation awaits the return of its most well-known and polarizing political figure, supporters and opponents debate the potential impact of Aristide on the most important vote in a generation and Haiti’s fragile political stability.

“While Aristide’s return may be a destabilizing force in the political environment, it is an opportunity to further test the judicial system, to address the rule of law, to confront painful issues that we frequently choose to avoid,’’ said Michel Eric Gaillard, a Port-au-Prince-based analyst. “This is a good test for democracy.”

In January, former dictator Jean-Claude Duvalier unexpectedly showed up at the Port-au-Prince international airport after 25 years in exile in France. He now faces human rights and corruption charges.

Some here question whether Haiti can afford the risk. Since Aristide’s Feb. 29, 2004 ouster amid a bloody rebellion, the country has struggled with armed kidnappings, deadly hurricanes, food riots and the hemisphere’s worst natural disaster — a 7.0-magnitude earthquake that left 300,000 dead, an equal number injured and one million-plus livingin tents.

“He’s a former president who is well-known and popular, and the people will be happy to see him. I don’t see any negative impact,” said Jean-Henry Ceant, a close ally of Aristide and among a group of losing presidential candidates still demanding cancellation of the flawed Nov. 28 elections.

The fact that Ceant and other Aristide-allied presidential candidates failed to generate support from so-called Aristide supporters speaks to the lack of weight he carries, said Jocelyn McCalla, a longtime Haiti observer in New York who formerly headed one of the largest Haitian-American rights groups.

“Folks keep looking for a Messiah and he plays the part real well, except he can’t keep up the act,” McCalla said.

Aristide, 57, arrives with no guarantees from Haiti, says the Haitian government and others privy to the planning of his trip. His request for 60 armed police officers was turned down. Under a law passed in his absence, former presidents are only entitled to five years of state-sponsored protection.

Questions about whether Aristide will face criminal charges also linger.

Following his ouster, Haiti’s U.S.-backed interim government issued four blistering reports from two government investigative commissions, including one led by Haiti’s current Minister of Justice Paul Denis. The reports alleged that Aristide had embezzled more than $20 million of his country’s meager public funds for the benefit of his private charities, his political party and several private firms that existed only on paper. But the investigations stalled. His lawyers have always denied the allegations.

At the same time, Aristide was under investigation by a Miami federal grand jury reviewing allegations of ties to narco-traffickers. Federal sources told The Miami Herald the five-year statute of limitation has run out on any potential money laundering charges stemming from the U.S. Drug Enforcement Agency’s investigation into alleged drug traffickers’ kickbacks to Aristide and other Haitian officials. For now, the government is mum as the country focuses on Sunday’s elections amid concerns over recent election violence.

Earlier this week, both Manigat and presidential rival Michel Martelly, a singer known as “Sweet Micky,” dismissed fears over his return. They each welcomed him back, with Martelly saying he will have no influence on the outcome of Sunday’s balloting.

Yet some believe that Martelly, a strident Aristide opponent who has been courting his base with populist rhetoric, may have the most to lose should the ex-president call for a boycott or endorse Manigat.

Aristide has said he has no political ambitions and plans to work in education — an assertion some doubt, citing his insistence on needing to return to Haiti before Sunday.

“He remains relevant for the time being in his ability to create mischief, hence his efforts to return before elections, and in a return to deep polarization,” said one diplomat who asked for anonymity because of the sensitivity of the topic. “He also has a lot of scores to settle.”

Miami Herald staff writers Jay Weaver contributed to this report from Miami and Lesley Clark from Washington, D.C.