It’s interesting that Lincoln had tendered to Stephen Douglas an appointment as a major general in the Army before Douglas’s illness and death; Douglas also appeared to be reasonably supportive of Lincoln’s policies as well.
This wasn’t unusual. Lincoln appointed influential “political generals” as a direct tactic to shore up Democratic support for the war effort. Benjamin Butler, for instance, was a prominent anti-Secession Democrat who was appointed a general in the Union Army in spite of almost zero military experience.