This might be a common topic to talk about, but my take is slightly different. It assumes the state legislature of Illinois is much more pro-Republican already, averting the issue. Lincoln becomes a Senator in 1859 as a result. I am somewhat familiar with his illness and he is two years younger, not the President, and the U.S. is not at war at this time. What I am most interested in is would he do as a Senator at this time. I would like to, but not to elaborate, hear thoughts on the alt 1860 election where people like Seward and Douglas are likely to be candidates. Slavery obviously has to be mentioned, and foreign policy, especially regarding Spain(in relation to Cuba given the South wanted to annex it) is welcome.
There are much easier ways to have Lincoln win in 1858 than to have Illinois "somehow" be much more Republican already. (Why would it be? After all, it's in the Lower North, has a lot of southerners--and yet Fremont came close in 1856 and the state elected a Republican governor.
https://en.wikipedia.org/wiki/Illinois_gubernatorial_election,_1856 I think that's about as Republican as a state like Illinois could reasonably expected to be in 1856--more Republican than Indiana, anyway. And in any event, the apportionment of the Illinois state legislature favored the Democrats, since it did not take into account the growth of northern Illinois. That is why Douglas in OTL would have won in 1858 even if there had not been a single holdover State Senator, as I explained at
https://groups.google.com/d/msg/soc.history.what-if/GgIKHDCwhEo/hnMwYZTX-R8J)
In my post at
https://groups.google.com/d/msg/soc.history.what-if/GgIKHDCwhEo/e6bPSdyELF8J I suggest two ways Lincoln could have won anyway:
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ObWI: Democrats don't pull their "October surprise" in 1858: "the release of a letter by Kentucky Senator John J. Crittenden endorsing Douglas (274). Crittenden was the successor to Henry Clay, and his letter gave credence to Douglas's dubious claim that he, rather than Lincoln, deserved to inherit the mantle of the Great Compromiser. For old Whigs who were still unsure whether Lincoln embodied Clay's mild antislavery sentiment or was an abolitionist in disguise, Crittenden's letter tipped the scales and convinced them that the best way to protect against 'negro equality' was to return the Little Giant to the Senate (288). Lincoln, says Guelzo, believed that his campaign had suffered a 'last-minute tail dive' (299)."
So let's say that Crittenden (because of illness, some sort of grudge against Douglas, or whatever) doesn't write the letter, and Lincoln is elected Senator. As the slayer of the "Little Giant" Lincoln is instantly mentioned as a Republican presidential candidate in 1860. Yet for that very reason might he actually be *less* likely to get the nomination in 1860, because his opponents within the party would be on notice? In OTL, they underestimated him until it was too late... (Still, even if his opponents were better prepared to organize against him, the case for nominating Lincoln would be strong: Seward was too offensive to nativists and was widely if wrongly considerd radical on slavery, Chase had an even more radical reputation on slavery than Seward, Cameron was too corrupt and had litle support outside Pennsylvania, Bates was too conservative and would offend German voters because of his support for the Know Nothings in 1856, etc.) Of course Lincoln had once thought that a Senate seat would be the peak of his political career, and might not be too enthusiastic about running for president, but the pressures on him to do so--especially on the grounds that he was the only candidate who could win--would be enormous.
(An alternative POD for Lincoln winning in 1858: "He [Guelzo] notes that Republicans anticipated vote fraud on the part of Irish immigrants in the employ of the Illinois Central Railroad and explains that this concern was not an idle worry. The Illinois Central was beholden to Douglas and could deploy workers to vote in strategic districts and sometimes to vote repeatedly throughout the day." So suppose Lincoln somehow manages to outbid Douglas for Illinois Central support--perhaps with help from the Buchanan administration. "Indeed, Guelzo contends, for much of the campaign Douglas had good reason to regard Buchanan as more of a threat than Lincoln. That explains why Douglas would be so sensitive to the possibility of collusion between the administration and the Republicans to defeat him--a charge which, despite Lincoln's denials, was not without foundation, since William Herndon's brother was an adviser to the Buchanan organization.")