She then quoted the Chicago Tribune's editorial endorsing Jackson Jr. in 2012 because Halvorson was "alarmingly unqualified" to serve in Congress, and added that she is "The most conservative candidate running and was one of the most conservative Democratic members of Congress in all of Illinois."

Kelly's campaign responded to the endorsement by hitting Hutchinson for her own gun record.

"President Preckwinkle might be able to look past Senator Hutchinson's A rating from the NRA, but the voters in the Second District won't," the campaign released in a statement. "They want someone who will fight against the NRA not stand with them. Robin Kelly is the one candidate ready to stand with President Obama to bring common sense gun control to help families throughout Chicago and the Southland."

Recent polls show that Halvorson has clung to a narrow lead in the race because none of the other candidates have yet been able to coalesce support. More than a dozen Democratic candidates are running for the seat, though Hutchinson and Kelly appear to be Halvorson's strongest foes.

This post was updated at 6:10 p.m.