"At the end of the day, this has always been about getting Chicago moving in the right direction. And right now, I believe the best way to do that is to come together," Stanton said in a statement.
Stanton said he endorsed Alexi Giannoulias' campaign.
The Illinois Secretary of State announced his mayoral bid last week.
Current Mayor Brandon Johnson has not said if he will run for reelection in 2027.