The correct option is “Union soldiers, who mostly voted for Lincoln.”
In the US presidential election of 1864, Abraham Lincoln was reelected as president. Lincoln competed under the flag of the National Union against his former superior general in Civil War, the Democratic candidate, George B. McClellan. McClellan was the “candidate for peace,” but he did not personally share the ideologies of his party. The elections of 1864 took place during the Civil War, but none of the states loyal to the Confederate States of America participated.
Republicans loyal to Lincoln, in opposition to a group of Republican dissidents who nominated John C. Frémont, joined a number of Democrats in the war to form the National Union Party. The new political party was formed to accommodate the Democrats in the war. On November 8, Lincoln won by more than 400,000 popular votes and easily secured an electoral majority. Several states allowed their citizens who served as soldiers in the field to vote, for the first time in the history of the United States. Soldiers in the army gave Lincoln more than 70% of their votes. This was the first re-election since President Andrew Jackson in 1832. Lincoln’s second term ended 6 weeks after his presidential inauguration due to his murder.