Clement Vallandigham was an Ohio lawyer who became involved in state politics during the mid-1840s. On two seperate occassions, Vallandigham, a Democrat, ran against Fusion Party candidate Lewis Campbell for a seat in the United States House of Representatives. He lost both times. Valldingham was undaunted by his losses and, in 1856, decided to run for the seat yet again. Facing the opponent he had lost to in the previous two elections, Vallandigham faced fierce competition. After the election, Campbell was reported to have won by nineteen votes. A recount was ordered, and it was determined that Vallandigham had actually won the election by twenty-three votes.

Vallandigham served in the House for three terms before he was voted out of office. In the election of 1862, he was defeated by Republican military hero Robert Schenc with a whopping 1,250 votes, a sure sign of the times. As a Democrat, Vallandigham opposed Lincoln's decision to go to war with the South over secession. His outspokenness on the situation contributed to his electoral defeat.

See also http://www.ohiocivilwar150.org/omeka/exhibits/show/ohio-volunteer-infantry/bombardment-of-fort-sumter/vocal-opposition

Vallandigham was a well known "Copperhead." In 1861, after Lincoln declared war on the South, Vallandigham traveled to Columbus to urge other Democratic legislators not to support the war. After two years, the military began tiring of Vallandigham's anit-war exhortations. In 1863, his efforts prompted the passage of a bill, aimed at him, defining treason. General Ambrose Burnside, commander of the Department of the Ohio, issued General Order No. 38. :

The habit of declaring sympathy for the enemy will not be allowed in this department. Persons committing such offenses will be at once arrested with a view of being tried. . .or sent beyond our lines into the lines of their friends. It must be understood that treason, expressed or implied, will not be tolerated in this department.

The order carried the extra sting by conditioning that certain violations could be punishable by death. Valldingham and the Peace Democrats objected to the order and protested that it was a violation of civil liberties, specifically freedom of speech.

On May 1st, 1863 Vallindgham helped organize a rally in Mount Vernon, Ohio to publicly denounce the order. As Vallandigham and other Peace Democrats took the platform to speak, two of Burnside's officers were observing the rally and subsequently reported everything back to General Burnside. 

Only a few days after the rally, a company of soldiers arrested Vallandigham at his home in Dayton. He was accused of violating General Order No. 38 and was ordered to stand trial. Vallandigham was brought before a military tribunal where a case was made against him. Valladingham did not deny the charges but simply contended that the military courts had no jurisdiction over his case. The judges paid him no heed and sentenced him to a United States prison for the remainder of the war.

When President Lincoln heard of Vallandigham's sentence, he was fearful that his opponents and Peace Democrats across the North might rise up to prevent Vallandigham's detention. The decision was then made to exile Vallandigham to the Confederacy on May 25th, 1863.

After only a few weeks, Vallandigham left the South and sought refuge in Canada where he remained active in Ohio politics as a Peace Democrat. He even received the Ohio Democratic nomination for governor in the 1864 election. Several Peace Democrats asked President Lincoln on Vallandigham's behalf to let him return to the country. Lincoln's conditions for Vallandingham's repatriation was that he swear to support the Union war effort, but Vallandigham refused. In 1864, he violated the military court's order by returning to the U.S. but federal officials never sought to arrest him.

To find out more about Vallandigham before and after the Civil War visit http://www.ohiohistorycentral.org/entry.php?rec=389