Halvorson is running against Jackson in the Democratic primary for the 2nd Congressional District seat.
Halvorson called on Robert Blagojevich to shed some light on the letter he sent to the House Ethics committee last year. In that letter, Robert Blagojevich offered to testify about Jackson's alleged involvement in the sale of President Obama's former Senate seat.
Halvorson says Blagojevich should speak now before the voters go to the polls.
"I'm appealing to Robert Blagojevich to come forward and inform the voters of just what are those truths you know about Jackson and haven't talked about," said Halvorson.
Jackson has denied any wrongdoing. He has not been charged. However, the House Ethics Committee is conducting an investigation.