United States Senate elections, 1858 and 1859

Various dates

22 of the 66 seats in the United States Senate (with special elections)
34 seats needed for a majority

	Majority party	Minority party

Party	Democratic	Republican
Last election	34 seats	15 seats
Seats before	42	20
Seats won	13	8
Seats after	38	25
Seat change	4	5
Seats up	17	3

	Third party	Fourth party

Party	Know Nothing	Other
Last election	2 seats	4 seats
Seats before	4	0
Seats won	0	0
Seats after	2	0
Seat change	2
Seats up	2	0

Majority Party before election

Democratic Party

Elected Majority Party

Democratic Party

The United States Senate elections of 1858 and 1859 were elections which had the Republican Party gain five additional seats in the United States Senate, but the Democrats retained their majority. That majority would erode in 1860 with the secession of the southern states leading up to the Civil War. In Illinois, incumbent Stephen A. Douglas (D) and challenger Abraham Lincoln held a series of seven debates, known as the "Lincoln–Douglas debates."

As this election was prior to ratification of the seventeenth amendment, Senators were chosen by State legislatures.

Senate Party Division, 36th Congress (1859-1861)

In these elections, the winners were seated during 1858 or in 1859 before March 4; ordered by election date.

In these general elections, the winners were elected for the term beginning March 4, 1859; ordered by state.

All of the elections involved the Class 2 seats.

In this general election, the winner was elected for the term beginning March 4, 1861.

This election involved a Class 3 seat.

In this election, the winner was elected in 1859 on or after March 4; ordered by date.

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