PORT AU PRINCE, Haiti – Despite warnings from President Obama that his return could cause yet another tumultuous political development here, Jean-Bertrand Aristide, the twice exiled former president of Haiti, left his adopted home in South Africa on Thursday and headed back to Haiti.

Dressed in a navy blue suit with a tie of red and blue, the colors of the Haitian flag, Mr. Aristide, a former firebrand priest beloved by the poor but dismissed by others as corrupt, appeared briefly before his flight departed at 11:13 pm local time, reading from a prepared statement that was primarily in Zulu, one of South Africa’s principal languages.

"We experience sadness in leaving our dear friends, but on the other hand, we are delighted to return home after seven years,” he said. “In Haiti also they are very happy because they were waiting for us.”

Mr. Aristide, who left Haiti in 2004 under American pressure as rebels closed in on the capital, is expected to land in Haiti by midday Friday, only 48 hours before voters choose a new president on Sunday. The election, a runoff, was delayed by a political crisis over widespread fraud in the first round of voting in December.

With Haitian elections tense, fragile affairs in normal times, it remained unclear what effect Mr. Aristide, Haiti’s first democratically elected president, might yield on the country. He has said he is coming back just to work on his educational foundation, but Western diplomats working to keep him out were skeptical given the timing of his return.

He will be the second polarizing figure in Haitian politics to return in recent months: Jean Claude Duvalier, the former dictator known as “Baby Doc,” suddenly returned from exile in January and is living quietly here while courts iron out pending human rights and corruption charges related to his regime.

With the potential for the former archrivals on Haitian soil and the country already reeling from a political crisis it hoped to dispel with a peaceful election, Mr. Aristide’s return generated furious diplomatic negotiation, with the United States pressing for a delay in his arrival until after the election.

President Obama telephoned South African president Jacob Zuma to press his case, but to no avail. At the airport with Mr. Aristide was Maite Nkoana-Mashabane, South Africa’s minster of international relations and cooperation. She wished him "a safe and happy landing" before his plane took off.

President Obama reiterated his concerns through a spokesman. “The United States, along with others in the international community, has deep concerns that President Aristide’s return to Haiti in the closing days of the election could be destabilizing,” Tommy Vietor, a spokesman for the United States National Security Council said Thursday.

South African officials, who oversaw his residence and security, said they ultimately had no cause to hold him. But the South African government remained close-mouthed about the details of Mr. Aristide’s departure right up to the last minute; some members of the Aristide delegation, which included the actor Danny Glover, said they were uncertain about when or if the flight would leave.

The Haitian government issued Mr. Arisitde a diplomatic passport weeks ago and said there was no reason he could not come back. Mr. Aristide’s supporters have spruced up his former residence and banners declaring “Welcome Back President Titide,” using his nickname, have sprung up around here. Mildred Aristide said that she did not even know if the home was still furnished. "I hope there is a bed," she said before leaving.

Both candidates in the runoff, Mirlande Manigat, a former first lady, and Michel Martelly, one of the country’s most popular singers, have derided Mr. Aristide in the past.

But, in a sign of his continuing support here, particularly among the poor, they have both sought to neutralize their past opposition.

Ms. Manigat has said he could play a role in her government as an education adviser. A banner, evidently put up by Ms. Manigat’s backers, hangs near the airport, declaring “you have your mother, now your father is coming.”

While Mr. Martelly, who has vulgarly dismissed Mr. Aristide in song, now says he has the right to return.

Kenneth H. Merten, the American ambassador here, said of Mr. Aristide’s return: “He gets to choose whether he will play a positive role here and I hope that’s his choice.”

Mr. Aristide helped lead a popular revolt that ended the Duvalier family’s nearly 30-year dictatorship. He became president in Haiti’s first democratic elections in 1990, was soon ousted in a coup in 1991 but then returned to power in 1994 after the United States military forced out the military regime.

Mr. Aristide was reelected in 2000 in an election boycotted by the major opposition parties, and while he was beloved by the poor he was criticized by many for corruption, autocracy and the violent suppression of political opponents.

Amid an armed uprising, led in part by former members of the Haitian army that Mr. Aristide had disbanded, he left Haiti on Feb. 29, 2004. He has said American diplomats kidnapped him, but the United States has long denied the accusation.

Barry Bearak and Pooja Bhatia contributed reporting from Johannesburg