I had a post on this in 2017:
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We have recently discussed what would have happened if Abraham Lincoln had been elected to the US Senate in 1858. But what if he had been elected in 1855? The 1858 campaign with its famous Lincoln-Douglas debates has overshadowed the 1855 struggle where Lincoln came within a handful of votes of winning.
The background is as follows: [1] In February 1855 the Illinois General Assembly was to decide whether to re-elect Senator James Shields, a Democrat. Though Shields had an antislavery past, he had voted for the Kansas-Nebraska bill. The legislature had more Democrats than Whigs, but five of the Democrats were anti-Nebraska, and they held the balance of power. Their candidate was Lyman Trumbull, who had broken with Douglas over the Nebraska question. The pro-Nebraska Democrats were divided; those closest to Douglas favored the re-election of Shields, while others favored Governor Matteson. Before the vote, the five anti-Nebraska Democrats caucused and agreed that they would stand by Trumbull and vote for him as long as he had even a slight chance of being elected. The Whig caucus agreed to support Abraham Lincoln on the first ballot, but to allow its members to vote as they pleased on subsequent ballots. The pro-Nebraska caucus agreed to support Shields on the first ballot, with the understanding they would switch to Mattteson if Shields' prospects seemed hopeless. As summarized by Mark R. Krug in *Lyman Trumbull: Conservative Radical,* pp. 98-99.
"There were one hundred members, and the successful candidate needed fifty-one votes to be elected. On the first ballot Lincoln received 45 votes, Shields 41, Trumbull 5, and Matteson 1. The second and third ballots were inconclusive, with the five anti-Nebraska-ites voting for Trumbull. On the fourth ballot, Trumbull increased his vote to 11 and Lincoln's total dropped to 33, while the Nebraska group gave its 41 votes to Shields. The situation did not change on the fifth and sixth ballots. On the seventh ballot the Nebraska group switched to Matteson and picked up three votes to a total of 44. On the ninth ballot, Governor Matteson increased his lead to 47, and most Whigs and Know-Nothings switched from Lincoln to Trumbull, who received 35 votes. Lincoln got 15 votes. It was clear that unless the Trumbull and Lincoln forces united, Matteson would be elected. Lincoln, who was in the lobby, sent his manager, John T. Stuart, who was Mrs. Lincoln's cousin and his former law partner, to confer with the anti-Nebraska men to ascertain whether they would consider voting for him. Stuart was informed by Palmer, Judd, and others that they could not vote for Lincoln, because they were pledged by the decision of their caucus to stick to Trumbull and considered themselves to be instructed by their constituents to vote only for an anti-Nebraska Democrat. In addition, they felt that since the majority of the legislature was Democratic, a Democrat should be elected. After hearing Stuart's report, Lincoln instructed his friends to vote for Trumbull, who was elected on the tenth ballot after receiving no more than the minimum of 51 votes. The announcement of Trumbull's election was received with 'prolonged cheers throughout the Hall'..."
Lincoln has been much praised for his "magnanimity" in throwing his support to Trumbull. William Herndon was to write "The student of history in after years will be taught to rever [sic] the name of Lincoln for his exceeding magnanimity in inducting his friends to abandon him at the critical period and save Trumbull, while he himself disappeared beneath the waves of defeat..."
https://books.google.com/books?id=NmYqAAAAYAAJ&pg=PA46 As Mark Krug (p. 101) noted, this was touching and poetic but not accurate: "The fact was that Lincoln, unless he was prepared to send Matteson to the Senate, had no choice but to direct his remaining supporters to vote for Trumbull. It was not magnanimity but a sound assessment of the political situation and of the prospects for his own future career that made Lincoln do what he did." (Mrs. Lincoln did not share her husband's "magnanimity" and openly expressed her resentment of Trumbull. The election ended her friendship with Julia Jayne Trumbull. The election also caused a life-long animosity between Trumbull and Judge David Davis, who would be Lincoln's manager at the 1860 Chicago convention. As he put it, "46 men should not yield their preference to 5.")
Anyway, it is arguable that Trumbull's election was best from the viewpoint of the future Republican party, because in a state like Illinois, where Democrats outnumbered Whigs, it was essential that the new party get Democratic support. (Not that either Lincoln or Trumbull wanted a new party in 1855--they both hoped that their respective "old" parties could become the vehicle of anti-Nebraska sentiment.) And it is certainly true that Trumbull's election upset Douglas more than Lincoln's would have--especially since Trumbull in 1855 still claimed to be a Democrat. But what if Lincoln had won? Davis later said that if he had been there, he could have caused the Whigs to be more stubborn in supporting Lincoln instead of starting to break for Trumbull, and let's say that the Whig solidarity combined with the fear of electing a pro-Nebraska man causes the Anti-Nebraska Democrats' united front to crack--with defections to Lincoln?
Of course in that case we would not have had the famous Lincoln-Douglas debates of OTL. But Lincoln would still debate Douglas--in the Senate! Indeed, this was what Trumbull did in OTL. In fact, in an 1856 Senate debate Trumbull even asked Douglas the famous Freeport question Lincoln was to ask two years later: "Trumbull asked Douglas whether or not he believed that the people of a territory could lawfully exclude slavery prior to the formation of a state constitution, and whether or not a slaveholder had a right to take and hold slaves in a territory in the absence of municipal law on the subject. Douglas in reply dodged a direct answer and asserted that only the Supreme Court could decide the question.38 If Douglas' answer did harm to his Presidential ambitions in the South, the damage was done in the Senate in 1856." Krug, p. 127. No doubt Lincoln would have asked Douglas the same question in the Senate. It was in fact a completely obvious question to ask, since it exposed the differences between northern and southern supporters of the Kansas-Nebraska Act.
In OTL, Lincoln got a substantial number of votes for vice-president in the Republican national convention of 1856. Might he have actually been nominated for this office in 1856? (If he had been, it is conceivable that Fremont would have carried Illinois, which he narrowly lost in OTL.) Less likely but not impossible: A deadlocked Republican national convention actually nominates Lincoln for president in 1856--and he wins! (He carries Illinois, and Whigs/Americans are more willing to go along with a "fusion" anti-Buchanan ticket in PA than in OTL...) Does the South secede? (Remember that he has not yet made his most "radical' speech, the "House Divided" speech. And many things that contributed to secession in 1860, such as Harpers Ferry, had not yet happened.)
In any event, even assuming he is not on the national ticket in 1856, Lincoln will be a much more familiar national figure in 1860 than he was in OTL. And it is unclear that he will run for president in 1860--he once said that he would rather have a full term in the Senate than be president. But in view of the weaknesses of all the other candidates--Chase was too radical, Seward was *seen* as too radical and was opposed by the nativists, Bates was too conservative, etc.--I would hardly count Lincoln out.
(Another question: who will run against Douglas in 1858?..)
[1] See
https://quod.lib.umich.edu/j/jala/2629860.0014.203/--senator-abraham-lincoln?rgn=main;view=fulltext for a fuller account
