Daniel Biss secured a commanding lead in the Illinois 9th District House race due to the district’s strong Democratic lean, reflected in its Cook Partisan Voter Index rating and consistent support for Democratic candidates since 1946. As the open seat successor to retiring Rep. Jan Schakowsky, Biss benefited from his background as Evanston mayor and former state legislator, a competitive but successful primary win among 15 Democratic contenders, and endorsements from key party figures. Republican nominee John Elleson, a repeat challenger with limited resources, faced structural headwinds in the heavily Democratic territory covering parts of Cook, Lake, and McHenry counties. Election results on November 3 showed Biss capturing roughly 79% of the vote, aligning with trader consensus at 100% probability; any reversal would require an unprecedented recount or legal challenge given the margin.