One of the offices up for election in 1858 was the U.S. Senate seat held by Stephen A. Douglas. Douglas criticized the Lecompton Constitution and President James Buchanan’s support of it in December 1857, causing a rift in the Democratic Party. Some Republicans were excited by Douglas’ repudiation of the Lecompton Constitution to the extent that they considered supporting his bid for reelection to the U.S. Senate in 1858. Although Douglas later denied it, he courted Republican support—meeting in person with prominent men such as Horace Greeley and hinting in correspondence to Republicans that he was finished with the Democratic Party. Lincoln and other Republicans were concerned by these developments and urged fellow party members to remain loyal in the upcoming election. In Lincoln’s view, Douglas disagreed with the Buchanan administration over whether the Lecompton Constitution accurately represented the will of Kansans, but did not repudiate the overall goal of admitting Kansas as a slave state.

Two days after the date of this letter, the Douglas and Buchanan factions of the Democratic Party in Illinois held separate conventions in Springfield. Lincoln and other Illinois Republican leaders observed the proceedings and held a conference that same evening. On the following day, the Illinois Republican State Central Committee issued a call to the counties of Illinois to select delegates to attend the 1858 Illinois Republican Convention in Springfield on June 16, 1858, the purpose of which was to nominate candidates for state treasurer and superintendent of public instruction, as well as to effect “the more perfect organization of the Republican party in Illinois.” At the June 16, 1858 convention Lincoln was nominated to challenge Douglas for the latter’s seat in the U.S. Senate.

In addition to this report from Wentworth, the rumor of a letter by a Republican Congressman from Illinois expressing support for Douglas was also raised at the Republican meeting Lincoln attended in Springfield on April 21 following the conventions of the Buchanan and Douglas Democrats. The letter causing the controversy was written by Washburne to Charles L. Wilson on April 12, 1858. In it, Washburne wrote that in light of Douglas’ differences with the Democratic Party, he would consider welcoming him as an ally to the Republican Party, but that Lincoln must be the Republican Party’s candidate for the U.S. Senate in Illinois in 1858. Lincoln wrote Washburne on April 26, 1858 regarding the rumors, and the pair exchanged several letters in which Washburne sought to explain the misunderstanding and reassure Lincoln of his support.