One American presidential candidate was shaped by his family's rich heritage in the US Navy and the other by community organising in the disadvantaged neighborhoods of Chicago's South side. Those diverse backgrounds explain some of their profound differences.

Yet John McCain and Barack Obama, drawing on these formative experiences, have a common grain: a commitment to service and a determination to foster public-private partnerships to address some of the nation's social and economic ills.

This promise has the growing field of social entrepreneurs, already active in inner-city programs around the country, exuberant.

"We are over the moon with these candidates," says Vanessa Kirsch, the head of America Forward, an umbrella group of 85 of the most active social-entrepreneurial efforts. "They come at it from different perspectives, but both are totally committed to the concept of a new era of service."

Both men frequently talk about expanding this concept, most recently as the US celebrated Independence Day. Obama declared he would continue and broaden President George W. Bush's effort to assist faith-based organisations involved in anti-poverty programs.

Two major addresses on the issue — Obama's at Cornell College in Iowa last December and McCain's at his alma mater, the Naval Academy, in April — are notable for their different perspective and similar themes.

Declaring that "all lives are a struggle against selfishness," McCain, the son and grandson of admirals, said that in addition to military service and political life "there are many public causes where your service can make our country a stronger, better one than we inherited."

At Cornell College, Obama worried that America is "not keeping pace with the demand of those who want to serve," faulting Bush for not summoning bolder efforts during the unifying days after the September 11 terrorist attacks. He proposed a Social Investment Fund Network that would combine public, private and non-profit efforts to "leverage private-sector dollars to encourage innovation and expand successful programmes."

These are more serious initiatives than those under their predecessors. Bill Clinton started the successful AmeriCorps, a domestic Peace Corps that works with underprivileged kids, on cleaning up the environment and on Indian reservations. Still, it's predominantly a government effort.

Bush's faith-based initiative has considerable merit as recognised by Obama. Yet, as two of the White House aides who ran this program complained, Bush's political guru Karl Rove politicised it.

Social entrepreneurs are pushing a new paradigm that bridges partisan and philosophical divides. They address needs ranging from schools to job training to prison fellowship, with as much business-like emphasis on efficiency and effectiveness as on compassion. They advocate public-private partnerships that eschew stifling governmental bureaucracies and the social indifference of the market; the premium is on performance.

The best-known is Teach for America, which grew out of a college thesis of founder Wendy Kopp almost two decades ago. Today, there are 3,700 recent graduates of some of America's most prestigious universities who are teaching underprivileged kids for at least two years.

The programme and its founder are legends on campuses. Last year, there were almost 25,000 applications, including from about 10 percent of graduating seniors from those top colleges. No other institution invites this sort of fervor.

"If you go to Harvard or Yale or Spellman, kids are saying, `I want to be like Wendy Kopp,"' says Mark Nunnelly, the managing director of Bain Capital LLC and a big advocate of social entrepreneurship. "There is a lot of power in that notion."

Some of these efforts focus on one community. The Harlem Children's Zone is a non-profit group that serves more than 12,000 children and adults in New York on a host of issues. It seeks to rebuild "the very fabric of community life."

Year Up trains teenagers and young adults for half a year and gets them apprenticeships in top corporations for the other half.

"Everyone is held accountable," says Gerald Chertavian, the chief executive officer. "A huge amount of value is created both for business and the community."

Some of the better programs working with prisoners are directed by political conservatives and religious groups.

The biggest focus of social entrepreneurship is education. Jon Schnur runs one of the best ventures, New Leaders for New Schools, which recruits and trains principals for troubled inner-city schools. It is in nine cities and has 550 principals or about-to-be school heads. The $29 million budget is half-funded by public sources and half private.

There is a rigorous selection process and candidates go through a six-week training program, then spend a year as residents in training at an inner-city school. Within three years, New Leaders expects to place principals in half the Washington, D.C., public schools, whose chancellor, Michelle Rhee, is a Teach for America alumna.

In perhaps its boldest venture, New Leaders is placing principals in the Hurricane Katrina-ravaged New Orleans school system.

Schnur has the Rand Corporation do an evaluation of every New Leader principal with precise metrics on what improvements students have made and how it compares to other schools. At the vast majority of these schools, there is marked improvement. Yet the performance-obsessed Schnur says that's not sufficient.

"In 20 percent of our schools, there are dramatic gains," he says. "We're focusing on the 80 percent that are not getting dramatic results."

These idealists without illusions — a term once used to describe John F. Kennedy — see vast expansions of what works. Schnur calls it "a scaling success," using social entrepreneurialese.

A McCain or Obama, they believe, will use the bully pulpit of the presidency, leveraging federal funds to attract more corporate and non-profit support for programmes that show results.

"A serious effort to use public funds to leverage private monies with a national spotlight," says Bain Capital's Nunnelly, "is very exciting."

(Albert R. Hunt is the executive editor for Washington at Bloomberg News. The opinions expressed are his own.)