CINCINNATI (AP) — Long before Mitt Romney and Barack Obama wrestled over Ohio, it was also a crucial political battleground state for Abraham Lincoln. So much so that when he received word of the results of the state's 1863 elections, Lincoln said in a message: "Ohio has saved the Nation."

"Ohio was almost a civil war unto itself," said historian William B. Styple, whose latest book focuses on a Cincinnati politician who was an influential aide to Union Gen. George B. McClellan, who ran against Lincoln in 1864. "There was a lot of turmoil in that state."

Ohio was home to some of the Union's most successful generals, led by Ulysses S. Grant, William T. Sherman and Philip Sheridan, as well as Lincoln's secretary of war, Edwin Stanton, and treasury secretary, Salmon Chase.

Lincoln brought Chase into his Cabinet after the former Ohio governor lost his bid for the Republican nomination in 1860 to Lincoln, as recounted in Doris Kearns Goodwin's best-selling book "Team of Rivals: The Political Genius of Abraham Lincoln." Much of Stephen Spielberg's new "Lincoln" movie, opening widely Friday, is drawn from the book.

But Ohio also was a home to McClellan, his adviser Col. Thomas M. Key, and other critics of Lincoln such as former U.S. Sen. William Allen and Rep. Clement Vallandigham. Vallandigham would lead the stridently anti-war "Copperhead" movement.

Many Ohioans, especially along the river, had roots, relatives and friends in Virginia or other parts of the South, and considered the issue of slavery a matter of states' rights. And even after Southern states seceded and Confederates shelled U.S. troops at Fort Sumter, S.C., there were differences in Ohio over the goals of going to war.

Historians say that some Ohioans worried the state would be flooded with newly freed slaves if the war resulted in emancipation, that there was sometimes-violent opposition to the federal army draft, and that others simply thought there should be more efforts at peaceful compromise.

"If you were on the north side of the (Ohio) river, in real time, during that war, you would have found a very, very deeply divided populace," said University of Cincinnati history professor and author Christopher Phillips.

Ohioans contributed to the Union Army in high numbers, and McClellan, Philadelphia-born but a Cincinnati resident who was Ohio's militia commander, led some of the Union's first successful engagements of the war. Lincoln soon put him in command of the Army of the Potomac, which McClellan helped build up and train.

But McClellan, who warned that emancipation of slaves would undermine the Union effort, and Key, a Kentucky-born judge and lawyer in Cincinnati, were Democrats who had supported Stephen Douglas for president against Lincoln in 1860, Styple writes.

Historians say McClellan privately referred to Lincoln as "a gorilla," and Goodwin's book has accounts of McClellan keeping the president waiting, including once going to bed while Lincoln sat expecting to see him.

Lincoln grew impatient with McClellan for other reasons — the general's cautious approach to the war and failure to pursue Confederate Gen. Robert E. Lee's army after the bloody 1862 battle of Antietam in Maryland.

Styple was researching a biography of his New Jersey hometown's namesake — Union Gen. Philip Kearny, killed in another 1862 battle — when he found letters and accounts that led to his interest in Thomas Key. Continued...