Vallandigham got involved in politics at an early age, campaigning for the Democrats in the 1840 election.  He served as a delegate to the Democratic county convention the next year, and then was elected without opposition to the Ohio state legislature in 1845.  Two years later, he moved to Dayton to become a partner at a law firm, as well as editor and part owner of the Western Empire newspaper.  In 1849, Vallandigham became active again in politics, losing a race for judge.  Thereafter, Ohio Democrats nominated him for lieutenant governor (1851) and Congress (1852, 1854, 1856), but he lost every election.  He contested the last narrow defeat, and finally in May 1858 the Democratically-controlled U.S. House of Representatives disqualified enough Republican votes to give Vallandigham a victory.  It was bittersweet, however; Congress adjourned the next day, ending the term.  He was elected in the fall, though, by a slim margin, and then reelected in 1860.  After gerrymandering by the state legislature, he lost in 1862.

Vallandigham adhered to a Jacksonian philosophy throughout his political life—states’ rights, strict constitutional interpretation, low tariffs, and anti-national bank.  The conservative political philosophy of Edmund Burke and Presbyterian Calvinism were also major influences on his thought.  Although Vallandigham admitted that slavery was immoral, he opposed abolitionism on political and constitutional principles and resisted equal rights for black Americans on racist grounds.  He was a Unionist who repudiated secession; yet he also opposed the Union war effort and became a leader of the Peace wing of the Democratic Party (“Copperheads”). 

Vallandigham’s ardent, persistent criticism of the Lincoln administration and the war caused one of the major political controversies of the Civil War.  In 1863, Ohio’s military governor, General Ambrose Burnside, issued an order against public expressions of sympathy with the Confederate enemy.  Considering that policy to be a violation of the 1st Amendment’s protection of free speech, Vallandigham tested it by delivering a vitriolic speech condemning the military decree and “King” Lincoln’s war to free blacks and enslave whites.  Consequently, the former congressman was arrested, tried, and convicted in a military court.  The incident provoked outrage in the Northern Democratic press and undermined War Democrats’ support of the Lincoln administration.

Vallandigham appealed the case to the U.S. Supreme Court on a writ of certiorari.  In Ex parte Vallandigham (1864), the Supreme Court unanimously denied the petition, citing lack of jurisdiction, and thereby avoided the constitutional question of the military arrest and trial of civilians.  Lincoln commuted his prison sentence to exile in the Confederacy.  Vallandigham soon left the South for Canada, at which time the Ohio Democrats, infuriated over his arrest, nominated him for governor. He directed his campaign from Canada ("Canady" in this cartoon means "Canadian"), but lost overwhelming to the Republican nominee.  Woodward also lost the gubernatorial election in Pennsylvania.  

When Vallandigham returned clandestinely to Ohio in June 1864 and again began speaking out against the war, Lincoln told military and civilian officials to ignore him.  At the Democratic National Convention in Chicago in August 1864, Vallandigham was instrumental in convincing delegates to add a peace plank to their party platform.  The plank called for an immediate halt to the fighting, followed by peace negotiations between the Union and the Confederacy.  The Democratic presidential nominee, General George McClellan, repudiated the peace plank, but the Republicans used it to paint the Democrats as Confederate sympathizers.  Vallandigham campaigned for McClellan and Democratic candidates in Ohio, Pennsylvania, New Jersey, and New York, but his party lost both the presidency and more seats in Congress.

At the close of the Civil War, Vallandigham helped form the “New Departure” wing of the Democratic Party.  He and like-minded Democrats argued that their party could only return to power by accepting the results of the Civil War and Reconstruction as irreversible facts and by looking to the future.  While still holding to strict constitutionalism, states’ rights, low tariffs, and resisting racial equality in social affairs, Vallandigham supported moderate Reconstruction policies, civil service reform, a wealth tax, hard monetary policies, and labor-capital cooperation.  Running on those issues, he lost elections to the U.S. Senate (1867, 1869) and the House of Representatives (1868).