CHICAGO — U.S. Rep. Jesse Jackson Jr. was back at the Mayo Clinic for an evaluation Tuesday and possibly a longer stay, nearly two months after being released for treatment of bipolar disorder at the Minnesota hospital, his father said Tuesday.

“I don’t know how long he’s going to be there,” his father, civil rights leader Rev. Jesse Jackson, said.

The hospital confirmed Tuesday that Jackson was back at the facility in Rochester for a follow-up evaluation “to ensure he is on the path to properly manage his health.” The statement did not say much else.

His father said his son was at the clinic for a doctor’s visit, and a family spokesman said he would issue a statement after the evaluation.

The congressmen quietly went on medical leave in June, and his office released scant details until the Mayo Clinic confirmed nearly two months later that he had been treated for bipolar disorder and gastrointestinal issues.

Even though Jackson is facing re-election in November, he has made no public appearances since then. The only campaigning he’s done has been a recorded robocall to voters over the weekend where he asked for patience. But his wife, Chicago City Councilwoman Sandi Jackson, his father and two fellow Democratic Illinois congressmen who visited him Monday have all said they’ve encouraged him to take his time in coming back to work or the campaign.

One of those congressmen, U.S. Rep. Bobby Rush, said Jackson was preparing for a long stay at Mayo.

Questions about Jackson’s health — and the timing of his medical leave — have rippled beyond his Chicago-area congressional district. Neither his congressional spokesman nor family members have been forthcoming with updates, saying little beyond that he’s been seeing doctors daily since he was released from Mayo in September.

Jackson, 47, remains under a House Ethics Committee investigation about ties to imprisoned former Illinois Gov. Rod Blagojevich. And his medical leave wasn’t announced until days after a former Jackson fundraiser connected to the Blagojevich investigation was arrested on unrelated federal medical fraud charges. Since then, the Chicago Sun-Times has reported inklings of another federal investigation over congressional finance.

When he was first admitted, the Mayo Clinic disclosed that Jackson was suffering from Bipolar II, which is defined as periodic episodes of depression and hypomania, a less serious form of mania. He was released and returned to his family’s Washington home last month.

Soon after his return, his family put their Washington condo on the market for $2.5 million, in part they said to help pay for medical costs. They later took it off public listings because of the visitors coming to the home and fear of safety, his wife has said.

Jackson, who first took office in 1995 and captured every election in a strong majority since then, faces two little-know challengers on the ballot. He’s widely expected to win re-election.