Mitchell, however, was in Springfield during the protest. He says the demonstration will not change his support for same-sex marriage- even as black ministers spearhead efforts oppose the bill.
"The truth of the matter is, this has nothing to do with civil rights for the LGBT community," said Bishop Lance Davis, who opposes same-sex marriage.
"We're talking about civil marriage in a civil society. We're talking about the rights of free people in a democratic society to express freely who they love," said Mitchell.
Mitchell is one of only a handful of African American state representatives to publicly announce support for the marriage equality bill. After weeks of fielding robocalls- and sometimes re-elections threats from black ministers- 14 of the Black Caucus members are either against or undecided on the issue that could come up for a floor vote within the next 48 hours.
"I will make a decision one way or the other and it very well may be a game time decision," said Rep. Will Davis, D-Chicago.
Rep. Al Riley- who had been counted among the undecided- sounded like a yes vote on Wednesday.
"Government should not be in the position of discriminating against any of its citizens," said Riley, D-South Suburbs.
Still, the bill to legalize same-sex marriage appears stalled in the Illinois House. Gov. Pat Quinn has urged lawmakers to pass the bill that was approved by the Senate on Valentine's day, but House members face intense pressure from both sides of the controversial issue.
Meanwhile, the bill's sponsor remains optimistic.
"How I read this is when I put this up on the board, this is going to pass. This is what I know," said Rep. Greg Harris, D-Chicago.