Updated at 9:14 p.m.

President Obama’s top political advisor is not commenting on the ethics investigation into U.S. Rep. Jesse Jackson, Jr. The president is supporting Jackson in the upcoming Second Congressional District Democratic primary against a former congresswoman, Debbie Halvorson.

“Well, the president has endorsed him, primarily because there’s a long history of friendship between them,” David Axelrod said Thursday. “And Congressman Jackson was very supportive of the president when he ran for the U.S. Senate back in 2004. They’ve worked together on things.”

“That is a friendship and it reflects a friendship,” Axelrod added.

Jackson, of Chicago, faces a rougher than usual re-election this year, as the House Ethics Committee investigates his efforts to win a Senate appointment in 2008 from now-convicted Illinois Gov. Rod Blagojevich. The congressman denies any wrongdoing and has not been charged with any crime.

Axelrod had little to say when asked whether the association with Jackson is a risk for the president.

“I’m not going to enter into that discussion. You know, let that process run,” said Axelrod, who - when pressed - still declined to comment. “By engaging in the discussion, I am - in a sense - commenting on the validy or lack of validity of that, and I’m just not going to engage in that.”

Regardless, Axelrod said the president is unlikely to have much time to campaign for candidates other than himself.

“I think the best thing he can do for Democrats across the country is be the strongest, most effective presidential candidate he’ll be,” Axelrod said.

Still, the endorsement itself sends a message. Jackson’s campaign noted it has billboards up, showing the congressman and President Obama, side by side.

In an statement from her campaign, Halvorson said she is “one of President Obama’s biggest supporters and I always will be.”

“But, this race is about the people of the district,” said Halvorson, who served in the Illinois Senate with Mr. Obama. “And, their endorsement is the only one that matters on Election Day.”

Halvorson represented the old Eleventh U.S. House District for a single term, before losing to Republican Adam Kinzinger in the 2010 election. When congressional boundaries were redrawn last year, her home in south suburban Crete wound up in the Second District, which Jackson has represented since 1995.