05/24/2010 10:58 am ET Updated May 25, 2011

Jesse Jackson, Jr. Considers Endorsing Kirk Over Giannoulias In Illinois Senate Race

Even before he won his party's primary, Alexi Giannoulias' campaign for U.S. Senate has been beset by critics arguing that his candidacy was flawed. And while recent polls show that he's winning over more Illinois voters, many in the political establishment still believe Democrats should push him out of the race if they hope to win.

One political figure he still hasn't won over is Jesse Jackson Jr., the South Side congressman and son of the former Presidential candidate. In an interview with POLITICO, Jackson Jr. suggested that he might be endorsing the Republican candidate, Congressman Mark Kirk, in the race instead of Giannoulias.

"I like Alexi Giannoulias, but I have great respect for Mark Kirk and his service to the people of Illinois," Jackson told POLITICO.

Jackson and Kirk work together on the House Appropriations Committee, on which both are senior members of the subcommittee that provides foreign aid.

It's exceedingly rare for a lawmaker of one party to endorse a colleague of the other party -- particularly within the same state -- meaning Jackson lending his name to Kirk would be a bit of a shock to the political system and a blow to Giannoulias's campaign.

Jackson's endorsement wouldn't be entirely uncomplicated for Kirk. Buried deep in the POLITICO story is perhaps the most salient fact about Jesse Jackson Jr.'s position in Illinois politics right now: his ties to Rod Blagojevich.

As the scandal unfolded in late 2008, it was revealed that Jackson was "Senate Candidate 5," one of the figures Blagojevich considered for the Senate seat to be vacated by Obama. Blagojevich is accused of trying to sell that seat, and while Jackson has acknowledged that the governor discussed his name, he maintains that he never made any illegal offers of quid pro quo in exchange for appointment.

Either way, Blagojevich's trial is set for this summer, which could mean things get messy for Jackson; as Rich Miller of the Capitol Fax blog points out, "his name is almost sure to be mentioned."

Ultimately, the endorsement might be a negative for Kirk. Jackson's South Side constituents are strongly Democratic, and will likely vote for Giannoulias regardless of Jackson's endorsement. And being seen with the scandal-tainted congressman might cost Kirk votes in the moderate suburbs.

But in the political realm, perception is everything, and having Jackson endorse Giannoulias' opponent would not be good for the Democrat.

The Giannoulias campaign had no comment on the POLITICO story.