On Monday, Sen. Dick Durbin (D-Ill.) said the congressman needs to come forward and explain himself to voters soon, the Chicago Sun-Times reported. "As a public official," Durbin said, "there comes a point when you have a responsibility to tell the public what's going on."
Adding to the mystery is that one of Jackson's former fundraisers, Raghuveer Nayak, was arrested by the FBI on suspicion of bribing doctors just four days before the congressman's office announced the medical leave.
While there's no indication the probe has anything to do with Jackson, the ex-fundraiser has been a problem for him ever since Nayak linked him to the corruption scandal that sent former Illinois Gov. Rod Blagojevich to prison for 14 years.
Congressional investigators are still looking into whether Nayak offered at least $1 million to the governor's campaign if Blagojevich would only appoint Jackson to the U.S. Senate seat vacated by Barack Obama's election to the presidency.
Despite the investigation, Jackson easily won his party's primary in March with more than 71 percent of the vote. He is set to face Republican challenger Brian Woodworth in November.
At this point, it's unclear whether Jackson will make it that far. The unusual circumstances prompted columnist Phil Kadner to speculate in the Sun-Times whether Jackson is secretly suffering from some sort of dire physical condition. He cited anonymous sources "close to Jackson" who tried to assure him the congressman would recover and run for re-election, but they also admitted they had no idea where he was or whether he was even in a hospital.
The congressman's office isn't helping clear things up, either. On Thursday, in the latest vague statement, his staff described Jackson's condition as "more serious than we thought" and that it had to do with "certain physical and emotional ailments." They said doctors ordered him into "in-patient treatment" but declined to explain where that was.
That's a far cry from the way the staff of his fellow Illinois delegate, Sen. Mark Kirk (R-Ill.), reacted after their boss suffered a stroke in January. Kirk's office has offered frequent updates on his progress and even allowed his doctors to be interviewed by reporters. The senator is expected to recover.
Meanwhile, Jackson's wife, Chicago Alderman Sandi Jackson, was confronted by reporters about her husband's whereabouts and also offered no real hint of his location or condition. Her statement just fueled more speculation about whether the congressman will be able to run in November.
"As a wife, my primary concern is that of my children," Sandi Jackson said, according to the Sun-Times. "I just want to make sure that they're taken care of, provided for."