The collapse of the Whig Party in American politics in the early 1850s created a fractured electorate that several new parties attempted to capitalize upon. One of these was the anti-slavery Republican Party while another was the American Party, also known as the Know Nothing Party. The American Party was an anti-Catholic, anti-immigrant, nativist party that saw mild success, although the party was never able to elect any members to national office. In 1856, former members of the largely defunct Whig Party drifted between the Republican Party, the American Party, and, to a lesser extent, the moderate wing of the Democratic Party. See the 1856 Federal Election. By 1858, former members of the Whig Party as well as the American Party were an important source of votes for both Democrats and Republicans in Illinois’s local and federal elections, and both Lincoln and Douglas worked throughout the campaign season to garner their support. Although John Bell was not a member of the American Party, his support would aid any candidate that he endorsed by swaying the votes of those American Party members that were part of the former Whig Party. Bell, running as a Constitutional Unionist, would run against and lose to Lincoln in the 1860 Presidential Election.

In the state’s local elections, Republicans won a majority of all votes cast in the state, but pro-Douglas Democrats retained control of the Illinois General Assembly, which elected U.S. senators in those days, and Douglas ultimately won reelection to the U.S. Senate. Through the campaign, however, and in particular through his participation in the Lincoln-Douglas Debates, Lincoln gained recognition as well as standing within the national Republican Party.

Bell neither wrote a letter or delivered a speech on behalf of Lincoln during the campaign for Senate. And though he shared Douglas’s aversion for the Lecompton Constitution, Bell did not endorse Douglas. Crittenden did become embroiled, however, in the campaign. On July 7, 1858, Lincoln wrote to his former congressional colleague Crittenden of Kentucky to ask whether rumors of Crittenden’s support for Douglas were true. Crittenden was widely regarded as the natural successor to Henry Clay, and Lincoln worried that a Crittenden endorsement for Douglas would hurt his chances with his former Whig brethren in Illinois. Crittenden welcomed Lincoln's rise to political prominence, but had little sympathy with the Republican Party. Crittenden responded on July 29, assuring Lincoln that he was remembered favorably. Crittenden explained, however, that he and Douglas, though always belonging to different political parties and "opposed, in politics, to each other," shared a strong aversion to the Lecompton Constitution. The Buchanan administration's harsh response to Douglas and use of its power to prevent his reelection brought sympathy from Crittenden. He wrote of Douglas, "I could not but wish for his success— and his triumph over such a persecution– I thought that his re-election was necessary as a rebuke to the Administration, and a vindication of the great cause of popular rights & public justice." Crittenden admitted that he had shared his support of Douglas in various conversations but that he had only sent a handful of letters in which "Mr Douglas was alluded to and recommended." Going forward, he wrote, he could not promise anything, only that, "Whatever my future course may be, I trust that I shall so act as to give no just cause of offence to any candid & liberal friend, even tho' he may differ with me in opinion."

Though expressing "no disposition for officious intermeddling" in his letter to Lincoln, Crittenden nonetheless became embroiled in election controversy. On July 19, T. Lyle Dickey, a former Whig and Lincoln supporter who had defected to the Democrats and Douglas, wrote Crittenden requesting that he confirm a conversation with Dickey in April 1858 where Crittenden praised Douglas. On August 1, Crittenden wrote Dickey confirming the conversation and his praise for Douglas's service to Illinois and his principled position on the Lecompton Constitution. Not wishing to be appear "to be an officious intermeddler" in the election, Crittenden requested that Dickey, should he speak of the conversation or letter, "acquit me of any intermeddling, or of the presumption of seeking to obtrude myself or my sentiments upon the attention of the people of Illinois." Dickey kept the letter private until October 19, when he read it aloud in a speech denouncing Lincoln for abandoning Clay and Whiggery. The Daily Illinois State Journal sought to mitigate the damage by claiming that Crittenden's letter to Dickey was a forgery and by suggesting that Crittenden had written Lincoln--presumably Crittenden's letter of July 29--supporting opposition against Douglas. The Daily Missouri Republican demanded that Lincoln publish this letter. The Illinois State Journal continued to misrepresent Crittenden's correspondence with Lincoln, prompting Owen G. Cates of Saint Louis to write Crittenden asking if he wrote such a letter. On October 28, Crittenden responded in a telegram: "I have written no such letter." Crittenden's letter to Dickey, Dickey's speech, and Crittenden's subsequent telegram hurt Lincoln in the old Whig stronghold of Central Illinois, contributing to Lincoln's loss to Douglas.