Retired General Wesley Clark is in Illinois to campaign for Democratic Senate candidate Alexi Giannoulias.
Clark is the former Supreme Allied Commander of NATO and ran for president in 2004.
He's scheduled to appear with Giannoulias at an electric-car recharging station in order to promote the candidate's energy policies and criticize Republican candidate Mark Kirk for backtracking on the cap and trade bill, according to the Chicago Sun-Times.
But Clark is likely to get asked about Kirk's military record, which has become an issue in the race.
Kirk, an intelligence officer in the U.S. Naval Reserves, has been accused of embellishing his military record, particularly regarding his service in Kosovo. Clark was an architect of the war there.
Polls have shown the candidates are in a dead heat for the seat once held by President Obama.