Senators were elected over a wide range of time throughout 1858 and 1859, and a seat may have been filled months late or remained vacant due to legislative deadlock.

The Republican Party gained five additional seats in the Senate, but the Democrats retained their majority.

Senator Stephen Douglas, a Democrat, defeated a challenge by former U.S. Representative Abraham Lincoln, the Republican nominee.

Lincoln, who had been a member of the Whig Party prior to 1856, attacked Douglas for his perceived subservience to the Slave Power, as evidenced by his support for the Kansas-Nebraska Act and the recent Supreme Court ruling in the case of Dred Scott v. Sanford.

Crittenden's support for Douglas considerably diminished Lincoln's chances of winning the election.

Further down ballot, Republican candidates for the state legislature collectively received 24,094 more votes than the Douglas Democrats.