1984 United States presidential election in Illinois

The 1984 United States presidential election in Illinois took place on November 6, 1984. All 50 states and the District of Columbia, were part of the 1984 United States presidential election. State voters chose 24 electors to the Electoral College, which selected the president and vice president of the United States.

Illinois gave its electoral votes to incumbent United States President Ronald Reagan of California, who was running against former Vice President Walter Mondale of Minnesota. Reagan ran for a second time with Vice-President George H. W. Bush of Texas, and Mondale ran with Representative Geraldine Ferraro of New York, the first major female candidate for the vice presidency. Reagan, who was born and raised in Illinois, had moved to California as a young man.

As of 2020, this is the last time a Republican presidential candidate won over 1 million votes in Cook County, the state's most populous county and home to Chicago. The presidential election of 1984 was a very partisan election for Illinois, with over 99% of the electorate voting only either for Democratic candidate Mondale or Republican candidate Reagan, though several other parties did appear on the presidential ballot in the State. Nearly every county in Illinois voted in majority for Reagan. One notable exception to this trend was Chicago's highly populated Cook County, which voted in majority for Mondale, albeit with a 2.6% margin, or 51% to 48.4%. Likewise, 1984 marks the last time any presidential candidate won Cook County with a single-digit margin, and the last election that a Republican won over a million votes in that county. Fulton, Henderson, Knox, Mercer, and Putnam Counties would not vote Republican again until 2016.

Illinois weighed in for this election as 4 percentage points more Democratic than the national average. , this is the last election in which Jackson County voted for a Republican presidential candidate. Reagan won the election in Illinois with a decisive 13-point landslide, carrying 96 out of 102 counties. No Republican candidate has received as strong support in the American Great Lakes States, at large, post-Reagan. While Illinois typically voted conservative at the time, the election results in Illinois also reflect a nationwide reconsolidation of base for the Republican Party which took place through the 1980s; Reagan called it the "second American Revolution." This was most evident during the 1984 presidential election. Notably, this is the closest to date that a Republican has come to carrying Cook County, home to Chicago, since Richard Nixon won it in 1972. Mondale took 51% of Cook County's vote to Reagan's 48.4%.

One of the electors initially gave his vote for vice president to Ferraro by accident, but fixed the mistake on a second ballot.

Primaries
The primaries and general elections coincided with those for other federal offices (Senate and House), as well as those for state offices.

Turnout
Turnout in the state-run primary elections (Democratic and Republican) was 37.25% with a total of 2,254,503 votes cast.

Turnout during the general election was 74.48%, with 4,819,088 votes cast.

State-run primaries were held for the Democratic and Republican parties on March 20.

Democratic
The 1984 Illinois Democratic presidential primary was held on March 20, 1984, in the U.S. state of Illinois as one of the Democratic Party's statewide nomination contests ahead of the 1984 presidential election.

Jackson's voters were 88% black, 10% white, and 1% were members of other groups.

Republican
The 1984 Illinois Republican presidential primary was held on March 20, 1984, in the U.S. state of Illinois as one of the Republican Party's statewide nomination contests ahead of the 1984 presidential election.

Counties that flipped from Republican to Democratic

 * Franklin
 * Gallatin
 * Rock Island