CHICAGO — In the cluttered office where he’s met with some of the nation’s top politicians and preachers, penned rousing speeches and planned civil rights marches, the Rev. Jesse Jackson speaks so softly — and with so little enunciation — that one strains at times to hear him.

At 71, he still keeps a hectic schedule and speaks extemporaneously on everything from voting rights to hostages in Gambia. But the head of one of America’s most prominent families struggles when addressing one thing: the son and heir to Jackson’s political influence who abandoned his congressional seat last week because of mental health problems and two federal investigations into his political dealings.

Sitting in his office — among photographs of mentor Martin Luther King — the elder Jackson’s body tenses, he sighs and his eyes drift off.

“My heart burns,” he told The Associated Press. “As I always say to my children, champions have to play with pain. You can’t just walk off the field because you’re hurt.”

Over the last 40-plus years, Jackson has played many roles — barrier-breaking presidential candidate, international hostage negotiator and master orator. There was a time when his presence alone inspired swift action and attracted throngs of reporters. Now it’s different.

These days, Jackson is more likely to seek out media attention rather than waiting for journalists to come to him. If his voice in national affairs is muted, it’s also because reporters don’t listen as closely as they used to.

“He’s not the magnet for the press he once was,” said David Bositis of the Washington-based Joint Center for Political and Economic Studies, who has known Jackson for years.

Associates and historians say it’s partly natural: Jackson is older, and the dynamics of civil rights activism have changed. His role as an inspiration for African-Americans has been altered by the rise of President Barack Obama and a new generation. But those who know him also attribute Jackson’s lower-key role to the last three years of troubles surrounding his eldest son. And some are concerned that the son’s woes could hurt the family’s image and legacy.

“Yeah, things might get damaged a bit,” said U.S. Rep. Danny Davis, a Chicago Democrat. “But you can’t erase the fact that Jesse Jackson Sr. has gone into foreign countries and brought back hostages that the state department could not get.” Jackson “has raised issues that nobody else would be raising at the time, and then ultimately other people would join in. And before you knew it, you had a movement.”

The reverend groomed his namesake for the public stage, giving him name recognition and helping launch his career. The younger Jackson introduced his father during the 1988 Democratic National Convention. They co-authored a book. When Jackson Jr. took office in 1995, he was viewed as a rising star with potential to seek the nation’s highest offices, following a trail blazed by his father. He held a spot on the powerful House Appropriations Committee and co-chaired President Barack Obama’s first campaign.

Then, in late 2008, everything began to change.

The investigation that toppled former Illinois Gov. Rod Blagojevich revealed that the younger Jackson may have been involved in discussions about raising money for the governor in exchange for an appointment to Obama’s former Senate seat. Jackson ceased almost all public appearances, and a cloud of suspicion hung over him, even though he has never been formally charged with any wrongdoing.

Legal proceedings also revealed that Jackson Jr. had had an extramarital affair, the same type of indiscretion that embarrassed his father almost a decade earlier. Jackson Jr. remained under a House Ethics Committee investigation until his resignation last week and still may face its final report.

Then earlier this year, just after the arrest of a former campaign fundraiser connected to the Blagojevich allegations, Jackson disappeared on a mysterious medical leave, which the family later said was for treatment of bipolar disorder.

While the father won’t address the son’s legal issues, he said it was difficult to watch his child struggling with the decision to step down, something doctors at treatment facilities in Arizona and Minnesota recommended immediately. He’s hopeful his son will recover soon and possibly return to public work.

In Chicago, questions are being asked about what political role the Jacksons will continue to play and whether they will try to influence who wins Jackson’s House seat in a special election slated for the spring. Another of the reverend’s five adult children, Jonathan Jackson, a Chicago State University business professor, is contemplating seeking the seat. Jesse Jackson Jr.’s wife, Sandi, a Chicago City Council member, has also been mentioned as a potential replacement, though she has remained conspicuously out of sight since her husband’s resignation.

No matter who replaces Jackson in Congress, the reverend will almost certainly have to address more questions about his son.

“They’re so tied to the hip, and I think that it will paint how people think of Jesse Jackson Sr.,” said Holly Campbell, a 49-year-old woman who lives just south of Chicago and has been a longtime supporter of the family.

His presidential runs inspired her to vote. But she’s felt something shift in her perception of the family, particularly after the allegations about the former congressman emerged. “I’m disappointed,” she said.

The elder Jackson is still busy, but his work often escapes notice. While he’s a sometimes-polarizing figure in the U.S., he is greeted in many places, including abroad, as an international statesman. He took credit for helping obtain the release of two Americans imprisoned in Gambia this year, though there was little international news coverage. During a recent protest about job-outsourcing with Illinois workers, Jackson intentionally got himself arrested for civil disobedience. His office supplied constant updates and photographs.

Jackson disputes that there’s been any slowdown in his activities. He says he can’t keep up with requests for help. Aides say 18-hour days aren’t uncommon as he continues almost monthly overseas trips, a regular newspaper column and weekly live broadcasts. He says he’s focused on equality and justice, as always, but he approaches things differently now.

Rather than organizing a rally for thousands of people, his work has moved into quieter areas, like the courts, often through his Rainbow PUSH Coalition, which he founded more than 30 years ago.

The Chicago headquarters is a virtual museum of Jackson’s life, including photo cutouts of King and Jackson and framed headlines showcasing his work freeing hostages. On a recent weekday, a crowd of people — including church leaders — waited to meet with him.

He spent much of 2012 working on the issue of challenges to voter rights across the country. He also visited a Wisconsin Sikh temple after a fatal shooting. And he returned several times to join the workers’ protests in northern Illinois.

Jackson acknowledges the changes in his tactics, news coverage and the wider world.

“The whole landscape has changed,” he said. “The rules are different today.”

That includes the nation electing and re-electing its first black president, which Jackson has complicated feelings about. He says he has always supported Obama — having voted for him for state senator, U.S. senator and twice for president. But he also takes some credit for Obama’s success, saying his own two presidential campaigns made it possible.

During the 2008 campaign, Jackson was caught on tape making crude remarks about Obama supposedly talking down to blacks. He apologized. The night Obama was first elected, Jackson was in the crowd at Grant Park, tears streaming down his face.

Jackson maintains that his family’s legacy won’t be damaged by his son’s problems.

“We’ve served in this country” for decades, he said. “I don’t think people are that fickle.”