Final answer:
War Democrats supported Abraham Lincoln, primarily because the Republican Party, renamed as the National Union Party, appealed to their desires to preserve the Union and work toward the abolition of slavery.
Therefore, the correct answer is: option "Abraham Lincoln".
Step-by-step explanation:
During the critical presidential elections of 1860 and 1864, the Democratic Party faced internal divisions over the issue of slavery.
The Republican Party, recognizing the need to unite and prevent a Union defeat, nominated Abraham Lincoln for president, with a platform that stressed abolition as a necessary component of peace.
To appeal to the War Democrats and ensure their support, the Republican Party changed its name to the National Union Party, nominating the 'former' Republican Abraham Lincoln and pairing him with the 'former' War Democrat Andrew Johnson as vice president.
These efforts culminated in successfully drawing support from many War Democrats who could back Lincoln's Civil War policies without directly supporting the Republican ticket.