Alexi Giannoulias leads the 2027 Chicago mayoral race in trader consensus at 54.5% implied probability, driven by his August 2026 campaign launch, roughly $22 million in cash on hand, trade union endorsements, and 53% voter excitement in University of Chicago polling. Incumbent Brandon Johnson, who formally announced his re-election bid on September 13 despite 23% approval and just 13.6% support for another run, trails at 12% amid a projected $882 million budget shortfall and criticism over spending and public safety. A crowded field of more than a dozen candidates, including Susana Mendoza at 13.5%, makes a February 23 first-round majority unlikely and positions a potential April runoff as the decisive stage. Early polling shows limited separation among challengers, with fundraising gaps and name recognition currently anchoring Giannoulias ahead in the market.