You got that right. There were “Copperheads” and all sorts of northern Dems who opposed the war, including George McClellan by 1864. Victor Hanson makes a nice point in a speech about how it depends on which year it was how “great” or “brilliant” Lincoln was. Right after Fredericksburg, a much higher % of northerners were “anti-war,” and after Gettysburg, a much higher were “pro-war.”
There is a clear parallel with the war in Iraq. After the overthrow of Saddam and the Ba'athist regime, we were involved in a stalemate for over three years. Americans are not fond of no-win wars in either the 19th or the 21st Century, and took it out on the Republican congress and in the governorships and the state legislatures in November 2006. After General Petraeus took command of operations and the surge began, the situation in the field turned around and the Democrat-run Congress has largely not challenged the Administration policy, despite its promises to do so in January 2007.
Sherman's taking of Atlanta in 1864 probably clinched Lincoln's victory in his bid for re-election. A clear victory in Iraq during the next two months will do likewise for McCain.