Lincoln named Andrew Johnson as his vice presidential running mate in 1864 because a. Lincoln had been severely disappointed in the performance of his first-term Vice President, Hannibal Hamlin. b. Johnson possessed the military and political shrewdness that seemed lacking in the Union cause.

Hannibal Hamlin was the vice president during Abraham Lincoln's first term in office (1861-1865). He had an overall good performance and was willing to run again. However, president Lincoln had other plans.

At the time, the United States was still in the midst of the Civil War (1861-1865), and people in the North were split between those who wanted to press on with the war and those who favored a settlement with the Confederacy. The Democratic Party in particular split into a pro-war faction and a pro-peace faction. Lincoln, feeling that his reelection wasn't secure, sought out a War Democrat to run as his vice-president, in order to entice pro-war Democrats to vote for him. Andrew Johnson was thus chosen as Lincoln's running mate. Even though he was a Southerner and a Democrat, he was loyal to the Union government and had a pro-war stance. Based on Johnson's performance as military governor of Tennessee, Lincoln also felt Johnson had the military and political shrewdness that seemed lacking in the Union cause.

The Lincoln-Johnson ticket won the 1864 United States presidential election in a landslide, winning 55% of the popular vote and 22 out of 25 states.