KAYONZA, Rwanda » Bill Clinton could not stop talking about soybeans. Over dinner in Kigali with a handful of longtime political aides and deep-pocketed donors, he recited the price of soy ("It never exceeded $8, and now it’s $16") and extolled its virtues as a miracle crop ("You can grow it with just a thin layer of topsoil").

The following day, he and his daughter, Chelsea, took a tour of a future soybean processing plant here, still a red-dirt construction site at the foot of misty green hills. Clinton swatted a fly out of his eye and predicted that demand would soar.

"The Chinese can’t drink milk, so they rely on soy," he said.

But when the manager at the plant asked him to return next year, when production will provide work to as many as 1,400 farmers, Clinton turned the subject to himself.

"I’m older than you," he replied. "We have to be sure I’m still around."

In conversations, Clinton frequently gives the sense that he feels as though he is living on borrowed time.

The world that Clinton now inhabits — the global philanthropist on a journey to cure the world’s ills and burnish his legacy — is far from the muddy terrain of partisan politics that he will return to on Wednesday night at the Democratic National Convention. In a speaking slot typically reserved for the vice president, Clinton will place Barack Obama’s name into nomination.

The invitation serves as a reminder of how far Clinton has come in four years to refurbish his image and restore his frayed relationship with the Democratic Party after Obama defeated his wife in the 2008 presidential primary campaign. And it shows how much Obama has come to rely on a predecessor he once denigrated to serve as both role model and validator.

For many Democrats, Clinton’s renewed stature and his appeal to rural and white working-class voters, a vital group that Obama has struggled to connect with, makes him both an ally of the current administration and a constant reminder of its political shortcomings.

"The excitement of ‘hope’ and ‘change’ aren’t what they used to be," said Hank Sheinkopf, a Democratic political consultant who worked for Clinton. "Bill Clinton represents the America Barack Obama needs to get back."

At 66, Clinton has outlived most of the men on both sides of his family, and in 2004 he underwent quadruple bypass surgery. The man famous for jogging to McDonald’s no longer eats meat or dairy products, and his skinny frame looks almost frail and unnatural carrying his outsize personality.

Confronting, perhaps, the prospect of a future without Bill Clinton, he is bringing his family deeper into the William J. Clinton Foundation, the charitable organization that he started in 2001. His wife, Secretary of State Hillary Rodham Clinton, has said she will return to charitable work after President Barack Obama’s first term, and his daughter has taken on a more active role in recent years.

"I told her, ‘Chelsea, you’ve got to suck it up if you want to have a life with a public impact,"’ Bill Clinton said.

A BREAKNECK TOUR

The visit here to the soy plant, partly financed by his foundation, was part of Clinton’s six-day tour in July to South Africa, Mozambique, Rwanda and Uganda. The roadshow gave Clinton, his daughter and a group of donors and aides who have been allied with the Clintons since their Arkansas and White House years a firsthand look at the philanthropic work that has consumed most of his post-presidential energy.

The trip had the singular feel of a Clinton campaign tour, with a breakneck schedule of speeches and meet-and-greets, Secret Service agents, a chartered Sun Country 737 and lots of Arkansas wisdom. ("We have a saying in Arkansas: If you find a turtle on a fence post, he didn’t get there by accident," Clinton told a group of bewildered nurses in Kigali.)

During the trip, the subject of his own presidency was a frequent one, but it is not always a nostalgic one. From the Rwandan genocide and the AIDS epidemic to famine and war in Somalia, Africa stands out as a source of conflict and regret for Clinton. Although his foundation has 1,300 employees and volunteers and works in 50 countries, nowhere is Clinton’s desire to right some of the wrongs of his presidency and proselytize Brand Clinton more evident than here.

The list of aides and donors who traveled with Clinton to Africa reads like the index of a Clinton family biography. The Clinton friends included Ira Magaziner, a key adviser in Hillary Clinton’s health care initiative in the 1990s who now runs the Clinton Foundation’s health division, called CHAI (short for Clinton Health Access Initiative and pronounced like the spiced Indian tea); Helen Robinson, a Little Rock friend who worked for Clinton when he was governor and held posts in the East and West wings in the Clinton White House; and Jonathan Orszag, the brother of former Obama aide Peter Orszag and an economic adviser in the Clinton administration.

But the trip also included donors like Andrea Catsimatidis, the daughter of supermarket mogul John Catsimatidis, and her husband, Christopher Cox, whose grandfather was Richard M. Nixon, who both support Mitt Romney in the coming election. Two other donors, Davis Sezna, the chief executive of a hospitality group, and his wife, Barbara, are also registered Republicans.

While traveling, Clinton frequently invokes his own time in office, peppering speeches with phrases like "in the 1990s" and "when I was president." He loves defending his foreign policy record so much that aides have turned it into a verb. "You got Black Hawked" means that Clinton cornered you, waved a long finger and defended at length his administration’s decision to intervene in Somalia.

But he does not Black Hawk anyone on Rwanda. He has said that not stopping the 1994 genocide, in which an estimated 800,000 Rwandans, mostly Tutsis, were slaughtered, was one of his main foreign policy failings.

"I don’t think we could have ended the violence, but I think we could have cut it down. And I regret it," Clinton told CNN during one of his stops in Rwanda.

Today, a plaque that reads "William J. Clinton Foundation" hangs at the entrance of the Kigali Genocide Memorial Center. Clinton helped raise the money to build the museum around a previously unmarked area where survivors took the remains of their loved ones.

Chelsea Clinton accompanied her father on each stop in Africa, shaking hands and introducing herself ("Hi, I’m Chelsea") along the way. The exposure is part of her deliberate evolution into a more public and less press-averse figure. In recent years, she has joined the boards of the Clinton Foundation, the Clinton Global Initiative and CHAI. In a blog post about the trip, she said she could not wait to go back to Rwanda.

"Hopefully next time with both my parents and Marc!" she said, referring to her husband, Marc Mezvinsky.

It is widely assumed that Hillary Clinton will join the foundation once she relinquishes her post as secretary of state. (Bill Clinton runs all of his potential meetings with foreign leaders by the State Department. As long as his wife holds office, the Clinton Global Initiative must hold its annual conference in the United States.)

"My mom is even more vehement in private than in public, if that’s possible, about leaving at the end of President Obama’s first term," Chelsea Clinton said. "She wants to go back to being a professional advocate for women and girls."

STRADDLING TWO WORLDS

A good deal of what Bill Clinton does at the Clinton Foundation and the Clinton Global Initiative is act as a broker between wealthy supporters, like the ones on this trip, and worthy causes. While his relationships with certain billionaires have drawn criticism, a big part of Clinton’s political nimbleness was his ability to shift between opulence and poverty.

In Johannesburg, he stayed at the Saxon Hotel, where he also stayed as president, when it was still the lavish private home of Douw Steyn, an eccentric South African insurance magnate. The hotel is also where Nelson Mandela went after prison to write his memoir, and several photographs of Clinton in his younger, plumper days hang on the walls.

"I always feel guilty about staying here," Clinton said as he looked around his private villa’s marble columns and army of obedient staff members. "But I get over it."

A couple of days later, a black SUV carrying Clinton, his daughter and Secret Service agents set off in a blinding cloud of orange dust before they made an off-the-schedule stop at a model village called Nyagatovu in rural Rwanda.

"I love this," Bill Clinton said as he explored Rwandan farm plots scattered with single-room houses with brightly painted doors.

"Let’s go look at the cows!" he said and slouched down in his suit to pet a slobbery brown dairy cow. "These people have the hardest job because the cows have to be milked every day, so they have no vacation."

He likes to use the Zulu greeting sawubona ("I see you") when he is traveling in parts of southern Africa, and he often received the response ngikhona ("I am here"). It is that sort of personal connection that helped him lure rural and working-class voters back to the Democratic Party in 1992, and it is that touch that many political analysts say Obama lacks, a perceived gap that Clinton said he had tried to help with.

"Suppose we’ve been friends for 40 years," Clinton said, putting a hand on a reporter’s shoulder.

He continued: "If you came to visit me in the hospital and said something pretty and eloquent instead of saying ‘God, I’m sorry. This sucks. I wish I could do more about it,’ it’s an insult."

"So I told the president the eloquence should go at the end of his speeches now, never in the middle," Clinton said.

In between espousing theories about how to solve Africa’s food shortage ("We need to do things Americans did literally 80 years ago during the Depression for farmers") and offering statistics about waterborne diseases ("80 percent of victims are under the age of 5"), Clinton often brought the conversation back to politics.

As he posed with tourists during a detour to Nicosia, Cyprus, Clinton yelled out for a reporter’s attention.

"These people are from the Netherlands," he said, putting his arm around a sunburned couple, camera phones in hand. "It’s the only country in the world with a 100 percent general health care mandate," similar to the one that his wife and Obama sparred about in the 2008 Democratic primary.

REGALING HIS GUESTS

After several stops in Rwanda, Clinton and his entourage took a short flight to Uganda. There he joined supporters for dinner in the verdant garden of the Kampala Serena Hotel, in Uganda’s capital city, the loud hum of locusts in the background. He had changed from the navy blue suit and pink dress shirt that he wore during the day into a casual guayabera-style shirt and khaki cargo pants. Typically, he changes outfits at least three times a day on his trips.

"He’s like Lady Gaga," one of his aides said.

At casual nightly dinners, his captive audience nodded when he ticked off obscure accomplishments ("In Arkansas, we went from 48 percent to 53 percent forested land when I left office") or praised Rwanda’s minister of health ["Obama could replace (Kathleen) Sebelius with her tomorrow, and I’d support it"].

If the donors get their money’s worth, Clinton makes sure that his charitable work does as well. On a visit to a primary school in the Mpigi District of central Uganda, a rural brickmaking area a half-hour outside Kampala, George Srour, the founder and "chief dreamer" of Building Tomorrow, a nonprofit group that helps bring schools to sub-Saharan Africa, told Clinton that he could use additional financing. Clinton pointed to Rumi Verjee, a wealthy Ugandan of Indian descent who lives in Britain.

"See that guy over there? He’s one of the most successful business people from Uganda, and he wants to give back," he said to Srour.

Clinton called out to Verjee: "Hey, Rumi, come over here. This is a shakedown!"

One day in Uganda, aides stood on the tarmac at Entebbe International Airport, giddily awaiting the arrival of Bill Clinton.

"Is that him?" Chelsea Clinton asked, holding a hand over her eyes as she watched a military helicopter emerge over the late-afternoon horizon.

When it landed, a slender 14-year-old Ugandan boy in his tattered school uniform shyly stepped out: Bill Clinton Kaligani. His mother named him after the former president when he visited Uganda in 1998. A photograph of Clinton holding the boy, as his wife looked on, wearing shoulder pads and a wide hat, hangs in their home in Chappaqua, N.Y.

"He was born the day before we got there," Clinton said minutes before he embraced the boy on the tarmac. "It was one of the most memorable days of my presidency."

Clinton agreed to pay his school fees, a move that some aides thought would set a bad precedent. Clinton did note that on the same 1998 African tour, a Senegalese farmer had named a goat after him.

"We’re going to fly the goat in next," he joked.

On almost every leg of the trip, the traveling entourage aboard the chartered 737 batted around political theories about Hillary Clinton’s chances of being elected president in 2016.

"If Romney wins, the party has to rally around her," said one donor who did not want to be named.

Bill Clinton grins when he thinks about his wife’s high approval rating.

"I think the country sees her the way those of us who know her see her," he said.

But on the subject of another presidential bid, he is more reserved.

"She points out that we’re not kids anymore, and a lot of people want to be president," he said. "But I think we need to let her rest, and I’d be for whatever she wants to do."

But Clinton clearly would like some role for both his wife and his daughter in guaranteeing the future of the foundation.

"We’re trying to build it up to make sure it’d still run if I drop dead tomorrow," he said.

© 2012 The New York Times Company