It was a long day's work for Bono (search), lead singer for the rock band U2 (search) and dedicated lobbyist for the world's poor and AIDS-stricken.

In Boston's FleetCenter on a Tuesday night, Bono and his band -- Larry Mullen, Adam Clayton and the Edge -- performed for a sold-out crowd, part of their 10-month, multicity tour of Europe and North America. Bono then rushed to the airport, arrived in Washington at 2 a.m. and five hours later set off on a busy schedule, trademark round shades firmly in place.

The musician joined Secretary of State Condoleezza Rice for a State Department lunch and talks about the upcoming meeting of industrialized nations, aid to Africa and the prospects for the foreign operations spending bill.

Next stop was Capitol Hill where Bono pressed several lawmakers, including Senate Appropriations Committee Chairman Thad Cochran, R-Miss., about increasing assistance for the poor. Bono was back in Boston for two more sold-out shows Thursday and Saturday.

If there is a familiar image of Bono, it is this. The Irish-born singer crisscrossing the stage, microphone in hand, as he leads a band that has enjoyed critical and commercial success for nearly three decades. The numbers are impressive even by rock stardom standards: some dozen albums, more than 120 million copies sold worldwide, 14 Grammy awards and sold-out concerts from Berlin to Philadelphia.

In Washington, Bono is more than a musician who, with his band, was recently inducted into the Rock and Roll Hall of Fame. Since 1999, he has been a persistent and often-successful lobbyist, persuading Republicans and Democrats, presidents and lawmakers, to provide millions to help end the scourge of AIDS (search), eliminate poverty in Africa and forgive Third World debt.

Bono's celebrity has opened the doors to the Oval Office and Capitol Hill suites. His knowledge of issues and his dedication have won over the Washington elite, some of whom found their 15-minute, meet-and-greet sessions turning into hourlong policy talks.

"I told him he's my favorite pest. He keeps coming back," said Senate Minority Whip Dick Durbin, D-Ill. "It's not unusual for members of Congress to be lobbied by stars and starlets. Usually it's a one-time stand. He's different. He clearly cares. He's clearly committed."

Said former House Majority Leader Dick Armey, R-Texas: "I don't assume that a rock star is going to be lucid on the esoterics of economics." He gave Bono an "A-plus" for being well-informed and intensely devoted to the issues.

Celebrities often make a splash in Washington, whether it's testifying on Capitol Hill on a headline-grabbing issue or posing with the president as Elvis did with Richard M. Nixon. Inaugurals, major presidential speeches and media fetes attract the glitterati and sports stars. A former actor named Ronald Reagan became president and his Hollywood pals made the capital a destination.

But Bono has displayed staying power. He pounds the hallways of Congress, meeting with lawmakers when he can. He calls Washington officials during breaks in recording sessions. He traveled to Africa with Treasury Secretary Paul O'Neill (search) in 2002 to draw attention to the plight of the continent's citizens. He enlisted the help of conservative Republican Jesse Helms, even though many in his music circle were aghast.

He's a rock star who can belt out U2 hits tinged with politics and religion, songs such as "Sunday Bloody Sunday" and "Pride (In the Name of Love)," to packed arenas. He also can tell the difference between an authorization bill and an appropriations measure. The former determines how much money will be spent; the latter provides the dollars.

"He's transcended music," said former Rep. John Kasich, R-Ohio, who met Bono through Arnold Schwarzenegger and later introduced the musician to Helms and Sen. Rick Santorum, R-Pa. "He's gone from a rock band to a rock band with a purpose."

Said Santorum: "He knows the importance of 302b allocations," the arcane congressional terminology that refers to amounts of money the appropriations committee doles out to each department and agency.

Through his involvement, Bono has set a standard for social activism that others may follow.

"Brad Pitt is studying closely how Bono works ... as is George Clooney," said Jamie Drummond, executive director of DATA.

DATA -- Debt, AIDS, Trade in Africa -- is a nonprofit group Bono founded in 2002 with Bobby Shriver, the Kennedy nephew and Schwarzenegger brother-in-law who helped the musician navigate Washington, and various activists to increase awareness of the crises in Africa. The recently announced Live 8 concerts and the One campaign that has brought together the likes of P. Diddy, Pat Robertson and Cameron Diaz to fight poverty is the result of what Drummond calls "leveraging the global entertainment industry."

When Bono lobbies in the capital, there are few of the trappings of fame. No limousines, no entourage. When he met with Rice for lunch, each had one assistant.

But occasionally the rock star persona breaks through. In 2002, in a Rose Garden ceremony in which President Bush announced a $5 billion, three-year foreign aid package, Bono flashed the peace sign at the press corps. In a 2005 book titled, "Bono, in conversation with Michka Assayas," the singer recalled Bush's reaction.

"The peace sign was pretty funny. He thought so too," Bono said. "Keeping his face straight, he whispered under his breath, 'There goes a front page somewhere: Irish rock star with the Toxic Texan."'

When Bono meets with lawmakers on Capitol Hill, and word of his presence spreads, fans line up with copies of CDs and albums to be autographed. At one meeting with Durbin, the senator was amazed at "how many members of my staff had a newfound interest in the Global AIDS initiative."

Bono, born Paul David Hewson 45 years ago, began his crusade in 1997 when he was asked to help out on the Jubilee 2000 campaign for complete cancellation of the debt Third World nations owed to richer countries. Greater involvement convinced Bono that he was "way out of my depth," and a tutorial with then-Harvard professor Jeffrey Sachs (search) soon followed.

In 2000, Bono lobbied to get $115 million for debt relief in the foreign operations bill. A year later, there was $435 million. More lobbying resulted in the AIDS initiative of $15 billion over five years and double the U.S. assistance for Africa.

"He's almost a statesman rather than a celebrity," said Shriver, a Santa Monica city councilman who remains on the board at DATA. "The young man's Nelson Mandela."