I don’t know if it’s true or not but I’d read that Lincoln was re-elected largely because of the military vote. Now this always sort of confused me because I’d read that “Little Mac” was extremely popular with his troops. On the other hand, by the time McClellan had been replaced and he was running on a platform or negotiated surrender, he might not have been quite as popular.
‘Little Mac’ was popular with the Army of the Potomac, but not the military as a whole. And when the 1864 election occurred, it was obvious that Lincoln, Grant, Sherman, et al, were in it to win. Even though Grant was entrenched at Petersburg, many in the North accepted it as merely a matter of time before the South was defeated.
And, yes, the Democrats, like today, were a party of compromise. I don’t believe the American public of that day, even with the carnage, was willing to trade 4 years of war for an easy peace.