Most Copperheads actively participated in politics . On May 1 , 1863 , former Congressman Vallandigham declared the war was being fought not to save the Union , but to free the blacks and enslave Southern whites . The army then arrested him for declaring sympathy for the enemy . He was court-martialed by the Army and sentenced to imprisonment , but Lincoln commuted the sentence to banishment behind Confederate lines . The Democrats nevertheless nominated him for governor of Ohio in 1863 . He campaigned from Canada , but lost after an intense battle . He operated behind the scenes at the 1864 Democratic convention in Chicago . This convention adopted a largely Copperhead platform and selected Ohio Representative George Pendleton ( a known Peace Democrat ) as the vice presidential candidate . However , it chose a pro-war presidential candidate , General George B. McClellan . The contradiction severely weakened the party 's chances to defeat Lincoln
1864 Democratic convention
1864 Democratic National Convention
Copperhead (politics)