1966 Illinois elections

Turnout in the primary was 32.20%, with 1,791,494 ballots cast (1,060,189 Democratic and 731,305 Republican).[1][2][3]

Turnout in the general election was 73.54%, with 3,928,478 ballots cast.[1][3]

Incumbent Senator Paul Douglas, a Democrat seeking a fourth term, was defeated by Republican Charles H. Percy.

All 24 Illinois seats in the United States House of Representatives were up for election in 1966.

Republicans flipped one seat, leaving the Illinois House delegation to consist of 12 Democrats and 12 Republicans.

1966 Illinois State Treasurer election

November 8, 1966
Turnout	70.01%[1][3]
Nominee Adlai Stevenson III Harris Rowe Party Democratic Republican Popular vote 1,889,595 1,849,940 Percentage 50.53% 49.47%
Treasurer before election William J. Scott Republican Elected Treasurer Adlai Stevenson III Democratic

Incumbent Treasurer was William J. Scott, a Republican. Democrat Adlai Stevenson III was elected to succeed him in office.

1966 Illinois Superintendent of Public Instruction election

November 7, 1966
Turnout	69.24%[1][3]
Nominee Ray Page Don M. Prince Party Republican Democratic Popular vote 1,999,279 1,699,367 Percentage 54.05% 45.95%
Superintendent before election Ray Page Republican Elected Superintendent Ray Page Republican

Incumbent Superintendent of Public Instruction Ray Page, a Republican, won a second term.

Seats in the Illinois Senate were up for election in 1966. Republicans retained control of the chamber.

Seats in the Illinois House of Representatives were up for election in 1966. Republicans flipped control of the chamber.

An election was held for three of nine seats for Trustees of University of Illinois.

The election saw the election of new Republican members Donald R. Grimes, Ralph Crane Hahn, and James A. Weatherly.[1][4]

Third-term incumbent Democrats Kenney E. Williamson and Frances Best Watkins lost reelection.[1][4] Incumbent third-term Republican Wayne A. Johnston Sr. was not renominated.[1][4]

Three ballot measures were put before voters in 1966. One was a legislatively referred state statute, and two were legislatively referred constitutional amendments.

In order to be approved, legislatively referred state statutes required the support of a majority of those voting on the amendment.[1] In order to be placed on the ballot, proposed legislatively referred constitutional amendments needed to be approved by two-thirds of each house of the Illinois General Assembly.[5] In order to be approved, they required approval of either two-thirds of those voting on the amendment itself or a majority of all ballots cast in the general elections.[1]

The County Officers' Re-Election Amendment, a legislatively referred constitutional amendment, was put to a vote. It would have amended Section 8 of Article X of the Illinois Constitution. It failed to meet either threshold for passage.[1]

General Banking Law Amendment was approved by voters as a legislatively referred state statute. It modified the state's banking law.[6] To pass, it had required a majority of those voting on the article to approve it.[1]

The Revenue Amendment, a legislatively referred constitutional amendment, was put to a vote. It would have amended Sections 1, 2, 3, 9, 10, 12, and 13 of Article IX of the Illinois Constitution. It failed to meet either threshold for passage.[1]