Well, someone might as well try 1912. It is not easy by any means though, and I probably don't have it exactly right, but here is my stab at it.
(I used a different shading system)
Roosevelt 224, Wilson 170, Taft 137
Here is my thinking:
In the >90% category, I put states that were already >50% and no manner of shifting votes among the other candidates would change the outcome of the state. This includes most of the south for Wilson and SD for Roosevelt.
In the >80% category, I put states where adding Taft's votes to Roosevelt's votes resulted in Roosevelt winning >50%, though only states where Roosevelt was actually leading. Includes only WA, MN, MI, and PA.
In the >70% category, I put states where adding Taft's votes to Roosevelt's votes resulted in Roosevelt winning >50%, and doing so resulted in Wilson losing the state. In addition, I included states where adding Roosevelt's votes to Taft's resulted in Taft winning >50%. This, however, is an assumption because having all of Roosevelt's votes would have gone to Taft under IRV is pure speculation on my part.
Now comes the hard part, allocating Debs's votes. For this map I assumed that Debs's votes would have split evenly between Roosevelt and Wilson, though a small fraction went to Taft in Roosevelt's absence. Doing so resulted in Roosevelt taking CA and MD very narrowly, and him taking NV, CO, and IN by wider margins. It also had Wilson taking AZ, OK, MO, and KY.
That took care of every state except for WI and OH. For both of the those states, Taft came in second and recieved Roosevelt's votes, but even giving Wilson all of Debs's votes did not see anyone reach >50%. However, in each case, Taft was within 1.5% of >50% while Wilson was further away. I do not know who Chafin's voters would go to, so for the sake of argument, I decided that a small percentage of Debs's voters would go to Taft, as he was closer to >50% than Wilson was in those two states.
Here is the simple state map:
Of course, the simple fact that they would be using IRV would through off the results entirely, so who knows what would have really happened. But this is my guess.
