The job is open because primary winner Scott Lee Cohen stepped down after allegations of steroid use and domestic violence surfaced.
The Democratic Party state central committee will select Cohen's replacement Saturday, but Quinn told ABC7 Thursday night why he'll speak out Friday.
"I think it is important I speak out before the vote on Saturday. I talked to just about all of the major candidates. I looked at backgrounds of all of the people that have gotten to this round and these are very good to have this open process," said Quinn.
More than 100 people applied for the lieutenant governor's opening. Party leaders picked 17 finalists last weekend.