Anticipating a potential wave election year for Democrats, President of the Cook County Board of Commissioners and Cook County Democratic Party Chairwoman Toni Preckwinkle made a focused effort to increase the Democrats' majority on the Cook County Board of Commissioners, focusing these efforts on three of the Board's four Republican-held seats. Preckwinkle-backed Democratic nominees ultimately succeeded in ousting Republican incumbents in the 14th and 15th districts, but fell roughly a mere 2,000 votes shy of unseating the 17th district's Republican incumbent.[3] Preckwinkle did not target the Republican-held 9th district seat, as the incumbent Republican, Peter N. Silvestri, was both popular and a political centrist and had a reputation for being a peacemaker on the Board at times when conflict arose between its members.[4] Democrats ran candidates for all seventeen seats, compared to the fifteen seats that the party had contested in the preceding 2014 election. Meanwhile, Republicans ran candidates for eight seats, and increase from the five seats they had contested in the 2014 election.
Seven new members were elected,[5] and ten incumbents were reelected. Three incumbents did not seek reelection. Four incumbents lost reelection, with two being defeated in primaries and the other two losing their general elections.
Two races saw seats change party, in both instances seeing an incumbent Republican losing to a Democratic challenger, creating a net gain of two seats for Democrats and a net loss of two seats for Republicans. Nine races saw a Democrat unchallenged in the general election.
Incumbent first-term Commissioner Richard Boykin, a Democrat, lost reelection, being unseated in the Democratic primary by Brandon Johnson by a margin of 0.88%. Johnson went on to win the general election unopposed.
Primaries
Democratic
Cook County Board of Commissioners 1st district Democratic primary[2]
Incumbent Commissioner Dennis Deer, who was appointed in 2017 to fill the vacancy left by the death in office of Robert Steele, won election to his first full term.
Primaries
Democratic
Cook County Board of Commissioners 2nd district Democratic primary[2]
Incumbent Commissioner Jerry Butler, a Democrat who first assumed the office in 1985, did not seek reelection. Democrat Bill Lowry was elected to succeed him.
Primaries
Democratic
Cook County Board of Commissioners 3rd district Democratic primary[2]
Incumbent Commissioner Stanley Moore, a Democrat who was appointed to the office in 2013 and was elected outright to a full term in 2014, won reelection to a second full term.
Primaries
Democratic
Cook County Board of Commissioners 4th district Democratic primary[2]
Incumbent second-term Commissioner John Fritchey, a Democrat, lost reelection, being unseated in the Democratic primary by Bridget Degnen, who went on to win the general election unopposed.
Primaries
Democratic
Cook County Board of Commissioners 12th district Democratic primary[2]
Incumbent Commissioner Sean M. Morrison, a Republican appointed in 2015 following the resignation of Elizabeth Ann Doody Gorman,[8] was reelected, defeating his Democratic opponent, Abdelnasser Rashid, by a narrow 1.14% margin in the general election.
Primaries
Democratic
Cook County Board of Commissioners 17th district Democratic primary[2]
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