The Democratic congressman from Illinois was released from the Rochester, Minn., clinic in September after seeking treatment for bipolar disorder and gastrointestinal issues. He has been with his family in Washington since, but has not appeared in public, campaigned beyond a recent robocall or said when he'll return to Capitol Hill. His spokesmen will only say that Jackson remains on the Nov. 6 ballot.
Jackson's father, a prominent civil rights leader, said the congressman will go back to Mayo in the near future, but would not say when or for how long. He said only doctors could determine if he would be able to return home immediately or receive further inpatient treatment.
"He has not regained his balance altogether," the elder Jackson said. "But he's seeking his balance."
He said his son has an "overwhelming desire to get back to work," but any predictions were premature.
Mayo Clinic spokeswoman Duska Anastasijevic said Jackson is not a current patient and she could not confirm whether he has plans to check into the clinic. Jackson spokesman Frank Watkins said he didn't have any further information.
Many questions about the congressman's medical leave have gone unanswered. He first took medical leave in June for what staff described as exhaustion, but the information wasn't disclosed publicly until two weeks later.
Since then, information has come in spurts. It took weeks for his office to say where and for what Jackson was being treated.
The timing of his leave also has invited scrutiny.
Jackson - just weeks from the election - remains under a House Ethics Committee investigation for links to imprisoned former Gov. Rod Blagojevich. The committee is looking into allegations that Jackson was involved in discussions about raising money for Blagojevich's campaign in exchange for an appointment to President Barack Obama's vacated U.S. Senate seat. And the announcement of the leave came just days after a former fundraiser connected to those allegations was arrested on unrelated federal medical fraud charges.
Jackson has repeatedly denied any wrongdoing and has said his name will be cleared.
More recently, the Chicago Sun-Times reported that there is a federal probe related to his campaign finances.
The congressman, who first won office in 1995 special election, faces two little-known candidates on the November ballot. He's widely expected to be re-elected to a ninth full term despite the fact that he has not appeared in public for months. Jackson's Chicago-area district is heavily Democratic and many community leaders and mayors have endorsed him.
Jackson has said recently that he sees doctors twice a day while at the family's home in Washington. His wife, Chicago Alderman Sandi Jackson, has said that only doctors will be able to say when he can return to work.
The congressman's first communication to the public since the leave came Saturday in a robocall to voters in which he asked for patience.
"I am anxious to return to work on your behalf, but at this time it is against medical advice, and while I will always give my all to my constituents, I ask for your continued patience as I work to get my health back," he said in the recorded call.
His opponents - a Republican college professor and postal worker running as an independent candidate - blasted the move.
"As we wait for the Congressman to return, we have no voice. And now the Congressman is saying he has no answer about when he will return," Republican Brian Woodworth said in a statement late Saturday.
Associated Press writer Sara Burnett contributed to this story.