Jackson resigned from office Wednesday after spending several months on medical leave. He was facing a House Ethics committee investigation into possible campaign finance infractions. He was elected to a ninth term earlier this month.
Halvorson was elected to Illinois's 11th district in 2008 but served just one term in the House before she was unseated by Rep. Adam Kinzinger (R) in the 2010 mid-term election. Prior to that, she was the first woman to become the first State Senate Majority leader.