Alexi Giannoulias, center, the Illinois Democrat running for President Barack Obama's old Senate seat attends U.S. President Barack Obama's speech to supporters at the Oakley Lindsay Center in Quincy, Ill., Wednesday, April 28, 2010. Obama visited Missouri, Iowa and Illinois to discuss the economy and his administration's policies. Illinois Secretary of State Jesse White is on the right. (AP Photo/Seth Perlman)
The first-term Illinois treasurer says Blagojevich's defense team subpoenaed him. Giannoulias is locked in a contentious race for President Barack Obama's old Senate seat with Republican Congressman Mark Kirk.
Kirk's campaign says the development is part of a "troubling pattern" with Giannoulias that includes regulators shutting down his family's Chicago bank.
Giannoulias says he introduced a friend of Obama's to a union official. The friend, Valerie Jarrett, allegedly was Obama's choice to replace him in the Senate after he was elected president.
Giannoulias' name was mentioned briefly last week during Blagojevich's trial.