It relies on an organizational structure of a ward or township committeeperson (until 2018 legal name change, "committeeman") to elect candidates.

By the beginning of the 21st century the party had largely ceased to function as a machine due to the legal dismantling of the patronage system under the Shakman Decrees issued by the federal court in Chicago.

"[2] The party was chaired by 31st ward committeeman Joseph Berrios from 2007 until April 2018, when Cook County President Toni Preckwinkle replaced him.

[5] Article IV, Section 4 of the By-laws of the Cook County Democratic Party allows the Suburban Vice-Chair (a position currently held by Illinois State Senator Don Harmon) the authority to "convene caucuses and meetings, solicit support for the organization, assist the County Chair in any matters upon request, coordinate activities concerning recommendations for endorsements of candidate, and bring before the Central Committee issues of particular interest.

[8] The careers of Irish Democrats from this period, such as John Comiskey from the Blue Island area, were still limited by anti-Irish discrimination.

[10] The local Democratic Party grew stronger in the decades that followed the Great Chicago Fire due in part to an influx of new immigrants from eastern and southern Europe.

He would come to dominate the organization for two decades and he was a national figure during the age when urban political bosses reached the height of their power and prestige.

[15][16] After Cermak's death, Patrick Nash and Edward J. Kelly consolidated the Cook County Democratic Party into a political machine.

[20][21] Arvey put reformers on the slate, such as Martin H. Kennelly for mayor, Paul Douglas for United States Senate, and Adlai Stevenson for governor of Illinois.

[23] The Shakman Decrees introduced judicial oversight of City and County hiring, reducing the number of voters who owed their livelihoods to the Democratic party.

[29] NBC News had televised the event and switched back and forth between demonstrators being beaten by the police in front of the convention hall and the festivities over Humphrey's victory inside.

[30] Racial tension over issues such as urban renewal in Woodlawn and Lincoln Park, red lining, open housing and public school desegregation alienated African-Americans and Latinos voters.

For a short while after Byrne's election Richard J. Daley's successor as Democratic County Party Chairman George Dunne supported her.

[36] George Dunne had a falling out with the mayor and in 1982 he lost the party chairmanship to 10th Ward committeeman Edward Vrdolyak, an ally of Jane Byrne.

[37] Latinos who had been displaced for years from the downtown and lakefront neighborhoods joined the West Town Coalition and the Young Lords, and both groups backed Harold Washington.

[46] Dunne did not seek re-election to the party chairmanship in 1990, amidst a scandal in which he admitted having sex with female county employees who alleged they were pressured into providing sexual favors to him.

[citation needed][52][failed verification] In July 2005, the federal court-appointed Shakman monitor reported widespread abuses of a previous court decree against patronage hiring.

[citation needed] On July 5, 2006, Robert Sorich, formally, Daley's director of the Mayor's Office of Intergovernmental Affairs and, informally, Daley's patronage chief, and Timothy McCarthy, Sorich's aide, were each convicted on two counts of mail fraud connected to rigging blue-collar city jobs and promotions.

[53][54][55][56] In 1995, Mel Reynolds, Democratic congressman from Illinois's 2nd congressional district, which includes parts of the south side of Chicago and south suburbs in Cook County and parts of Will and Kankakee Counties, was convicted on 12 counts of sexual assault, obstruction of justice and solicitation of child pornography, and while serving his sentence, was convicted on 16 unrelated counts of bank fraud, misusing campaign funds for personal use and lying to FEC investigators.

On February 1, 2007, Joseph Berrios was unanimously elected Chairman of the Cook County Democratic Party and headed the organization until April 18, 2018.

[62] Berrios has been the subject of numerous investigations and legal proceedings involving ethical violations, corruption, fraud and nepotism.

[4] Examples of high-profile cases which have resulted in the conviction of members of the Cook County Democratic Party include Rod Blagojevich, Isaac Carothers, Arenda Troutman, and Jesse Jackson, Jr.[67][68]