1918 United States Senate elections

Retirements Three Republicans and one Democrat retired instead of seeking re-election. Two Republicans retired instead of seeking election to finish the unexpired terms, one Democrat retired instead of seeking election to a full term and two Democrats retired instead of seeking election to finish the unexpired terms. Defeats Eight Democrats and one Republican sought re-election but lost in the primary or general election. Deaths One Democrat died on October 21, 1917, and his seat remained vacant until an April 1918 election. Post-election changes Source: United States Senate Official Website == Change in composition ==

Before the elections Elections results == Complete list of races ==

Special elections during the 65th Congress In these special elections, the winner was seated during 1918 or before March 4, 1919; ordered by election date. Elections leading to the 66th Congress In these general elections, the winners were elected for the term beginning March 4, 1919; ordered by state. All of the elections involved the Class 2 seats. == Closest races ==

Eighteen races had a margin of victory under 10%: == Alabama ==

Idaho (regular) Idaho (special) Incumbent Democratic Senator John Frost Nugent defeated Republican nominee Frank Robert Gooding by a very narrow margin of 1.00% and by 970 votes. Upon his election, John Frost Nugent became the first Democrat ever to have been elected to the United States Senate in Idaho or from Idaho and the first non-Republican to win a United States Senate seat in Idaho or from Idaho since 1901 and the first non-Republican to win the Class 3 Senate seat in Idaho or from Idaho since 1897. == Illinois ==

Louisiana (regular) Louisiana (special) == Maine ==

New Hampshire (regular) New Hampshire (special) == New Jersey ==

New Jersey (regular) New Jersey (special) == New Mexico ==

Oregon (regular) Oregon (special) == Rhode Island ==

South Carolina (regular) South Carolina (special) == South Dakota ==