The only US war leader who had to work with anything like the political situation Lincoln faced was, I'd say, LBJ.

Lincoln's political position in 1861 was far weaker than FDR's in 1941. as Director says, the USA was firmly behind FDR whereas Lincoln had to try to keep onside a spectrum of opinion from radical Abolitionists to Lower North Butternuts and Peace Democrats. Again as Director says, keeping Missouri, ...