Jackson, who is reportedly under investigation for possible misuse of campaign funds, left the clinic in Rochester, Minnesota on Tuesday, according to Nicholas Hanson, a Mayo spokesman.

"He and his family remain grateful for support and prayers offered and received on his behalf," Hanson said in the statement. Jackson is being treated for bipolar disorder, a psychological condition marked by extreme mood swings.

The news follows media reports that the Chicago Democrat has hired high-profile criminal defense lawyer Dan Webb to handle negotiations with the federal government on a possible plea deal.

In addition, The Wall Street Journal has reported that the investigation into possible spending of campaign funds to decorate Jackson's Washington, D.C. home has expanded to include Jackson's wife, Sandi, a Chicago alderman.

Federal authorities have not confirmed the reports.

Representatives of the Jacksons have not returned calls seeking comment. The alderman also did not appear Wednesday at a meeting of the Chicago City Council's human relations committee, of which she is a member.

Fox Chicago television reported Wednesday that she had texted the station saying that her husband's attorneys asked the family not to comment, adding: "It's killing me because 90 percent of this stuff is false."

Between 2001 and 2012, Sandi Jackson's consulting firm, J. Donatella & Associates, received nearly $472,000 from her husband's campaign. The biggest payments came in the 2011-12 campaign finance cycle, at $120,000 as of October 31, and the 2009-10 cycle, at $116,000, according to the website OpenSecrets.org, which compiles campaign financial data.

The Federal Election Commission has declared the practice of lawmakers employing relatives as legal for campaign committees. Sandi Jackson's campaign, Friends of Sandi Jackson, has received $242,012 from her husband's campaign since 2005, according to OpenSecrets.

Jackson, the son of civil rights activist and former presidential candidate Jesse Jackson, has been on medical leave from the U.S. House of Representatives since June and not been seen in public in an official capacity.

Jesse Jackson, Jr. did not campaign to retain the congressional seat he has held since 1995, outside of a "robocall" to constituents regarding his mental health issues before the November 6 election. He was easily re-elected to Congress.

In addition to his health issues, Jackson has been the subject of a House ethics committee probe over an alleged bribe offered by a Jackson supporter in 2008 to then-Illinois Governor Rod Blagojevich.

The bribe was said to be intended to entice Blagojevich to appoint Jackson to the U.S. Senate seat vacated by President Barack Obama. Jackson has admitted to lobbying for the seat, but denied knowing about any money offered to Blagojevich, who has since been convicted on corruption charges and imprisoned.

The last statement made by the House ethics committee on the Jackson probe was in December of last year, in which the committee said that it will continue to review the matter.

(Reporting by Mary Wisniewski and Marcus Stern, editing by Greg McCune, desking by G Crosse)

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