Durbin, 81, will retire next year after serving five terms in the US Senate.
Her victory on Tuesday came after months of trailing in the polls but she received an endorsement and a reportedly $12m cash injection from billionaire governor of Illinois, JB Pritzker.
Stratton sprung ahead by digging into her opposition of Trump’s immigration enforcement, directly calling for the abolishment of Immigration and Customs Enforcement (ICE).
Krishnamoorthi took a more measured stance in comparison, calling for the abolishment of “Trump’s ICE”.
In her victory speech in Chicago, Stratton said: “Courage inspired me to run. Courage powered this campaign and courage will bring this fight straight to Donald Trump’s front door.”
Turnout for this year’s Senate race was unusually high for a non-presidential year, with over 1.1 million votes tallied in the Democratic primary – on pace to exceed the 2004 primary, when Barack Obama was running for Senate.
If Stratton is elected, she would become the sixth black woman to serve in the Senate in its 237 years.
It would also be the first time three black women served in the Senate at the same time, as she would join Angela Alsobrooks and Lisa Rochester.