Illinois held a primary on March 17, 2020, and the state-level elections on the ballot included the state Senate, state House, state supreme court, and state appellate court. The general election is November 3, 2020. The filing deadline passed on December 2, 2019.

Twenty of the 59 Illinois State Senate seats are up for regular election in 2020. Three Democratic primaries and nine Republican primaries for those seats were canceled after no candidates filed. Of the 17 Democratic primaries that were on the ballot, six were contested races and 11 were uncontested races with only one candidate. Of the 11 Republican primaries that were on the ballot, two were contested races and nine were uncontested races with only one candidate. All 14 Democratic state Senate incumbents who ran for re-election advanced to the general election. No Republican state Senate incumbents ran for re-election in 2020.

Illinois also held a special primary for the District 11 seat in the state Senate on March 17. Democrat Celina Villanueva, who was appointed to the seat in January 2020, was the only candidate to file and advanced to the November 3 special general election.

All 118 seats in the Illinois House of Representatives are up for election in 2020. Sixteen Democratic primaries and 56 Republican primaries for those seats were canceled after no candidates filed. Of the 102 Democratic primaries that were on the ballot, 22 had contested races. The other 80 were uncontested races with only one candidate. Of the 62 Republican primaries that were on the ballot, eight had contested races. The other 54 were uncontested races with only one candidate. Nine state House incumbents—three Democrats and six Republicans—did not run for re-election in 2020. Of the 109 incumbents who ran for re-election, 107 advanced to the general election. Democratic incumbents Yehiel Kalish and Yoni Pizer lost their primaries. Both had been appointed to their positions, meaning this was their first election.

Two Illinois Supreme Court seats were on the primary ballot on March 17. The Republican primary for the 1st District race was canceled after no candidates filed. Incumbent P. Scott Neville advanced from the Democratic primary, defeating six opponents. In the Republican primary for the 5th District race, David K. Overstreet defeated John B. Barberis Jr. for a place on the general election ballot. He will face Judy Cates, who advanced from the Democratic primary after running uncontested.

The Illinois Appellate Court also held primaries on March 17 for three seats. The Republican primaries for the 1st Division and 3rd Division seats on the 1st District Appellate Court were canceled as no candidates filed. The results of the Democratic primaries for those seats were pending as of March 19, 2020. In the Republican primary for the 5th District Appellate Court, Mark M. Boie defeated Katherine Ruocco. He will face Sarah Smith, who ran unopposed in the Democratic primary, in the November 3 general election.

Ballotpedia also covered primaries in Cook County on March 17. The offices up for election included clerk of the circuit court, county state’s attorney, county board of review commissioner, county water reclamation district board member, circuit court judgeships, and subcircuit court judgeships.

Illinois has a Democratic state government trifecta. A trifecta exists when one political party simultaneously holds the governor’s office and majorities in both state legislative chambers. Democrats have a 40-19 majority in the state Senate and a 73-44 majority in the state House. Democratic Governor J.B. Pritzker was first elected to office in 2018.