WASHINGTON - In the first 200 years of the republic, just three presidents survived more than two decades after leaving office: John Adams, Martin Van Buren and Herbert Hoover. The odds for ex-presidents have improved considerably since then.

Jimmy Carter, who raised the bar for active post-presidential years, is 88 now, and 32 years out of office. No one has survived longer after leaving the White House. George H.W. Bush, 89, passed the two-decade mark this year. The two most recent former presidents, Bill Clinton and George W. Bush, both are going strong. Gerald Ford lived nearly 30 years after leaving office.

There's a lot happening in the ex-presidents club these days - thanks to increasing longevity, the personalities of the current members and expanding opportunities for influence.

After a relatively quiet start to his post-presidency, George W. Bush in recent weeks has made headlines by speaking out for immigration reform and popping up in Africa at a wreath-laying with President Barack Obama to remember victims of terrorism. Clinton, with his philanthropic work and a wife who's a potential presidential candidate, is never far from the news.

The elder Bush, although frail, was at the White House last week (in jaunty red-and-white striped socks) for a ceremony promoting the volunteerism program he started as president. And Carter, noted for his years of globe-trotting work to advance human rights, spoke out last week against "legal bribery of candidates" at home in the form of unchecked political contributions by outside groups.

Is all this activity the new model for ex-presidents? It turns out they've got plenty of examples to draw on from earlier centuries.

"There's a whole class of people who leave the White House and continue to take a hyperactive role in American life," says presidential historian Douglas Brinkley of Rice University. He points to Andrew Johnson, who was elected to the Senate after a presidency that included impeachment; William Howard Taft, who became a Supreme Court justice; John Quincy Adams, who was an outspoken opponent of slavery as a member of the House; Theodore Roosevelt, who created the Bull Moose Party and tried to regain the presidency, and many more.

"There is no rule of thumb," says Brinkley. "Each man is just different."

For all their differences, though, recent chief executives have tended to start their post-presidential years relatively quietly, taking time to regroup, to heal in some cases, and give the new guy space to operate. They focus on raising money for their presidential libraries/centers. They write memoirs. Their poll numbers improve as time passes and memories of hard-fought presidential battles soften.

Call that phase one.

Bush, whose presidential center in Dallas was dedicated in April and whose 2010 memoir, "Decision Points," was a best-seller, has seen his poll numbers rebound, and he seems to be entering phase two: He says he wants to make a difference in the world, but steer clear of politics and avoid meddling in Obama's business.

His recent activities have demonstrated both the possibilities and limitations of an ex-president's influence.

Bush's presence in Africa during Obama's visit to the continent offered a reminder of his efforts to fight HIV and AIDS there. But his entreaty to bring a "benevolent spirit" to the debate over immigration reform seemed to have zero impact on House Republicans. GOP legislators said Bush's comments never even came up in their closed-door meeting about immigration on the day he spoke out.

"We care what people back home say, not what some former president says," said Rep. Tim Huelskamp, R-Kan.

Still, recent ex-presidents seem to be assuming a higher profile in public affairs and politics, says Thomas F. Schaller, a political scientist at the University of Maryland-Baltimore County who has written a study of postmodern ex-presidents.

"The opportunities are greater," says Schaller, pointing to the bigger role of electronic media, the globalization of politics and the tendency of ex-presidents to work more cooperatively with one another and with the current occupant of the White House.

After Clinton and the elder Bush worked closely on humanitarian aid for victims of Hurricane Katrina and the tsunami in Indonesia, Clinton quipped, "People began to joke that I was getting so close to the Bush family, I had become the black sheep son."

A number of earlier ex-presidents also played on the global stage - but with a smaller megaphone.

Herbert Hoover, who lived nearly 32 years after his presidency, traveled the world and took on significant relief efforts in Europe during and after World War II. He later served on government reform commissions during the Truman and Eisenhower administrations, and declared he had "outlived the bastards" who blamed him for the Great Depression, according to Schaller.