Incumbent President Andrew Johnson had succeeded to the presidency in 1865 following the assassination of Abraham Lincoln , a Republican . Johnson , a War Democrat from Tennessee , had served as Lincoln 's running mate in 1864 on the National Union ticket , which was designed to attract Republicans and War Democrats . Upon accession to office , Johnson clashed with the Republican Congress over Reconstruction policies and was nearly removed from office . Johnson received some support for another term at the 1868 Democratic National Convention , but , after several ballots , the Democratic convention nominated Governor Seymour of New York . The 1868 Republican National Convention unanimously nominated General Grant , who had been the highest-ranking Union general at the end of the Civil War . The Democrats criticized the Republican Reconstruction policies , and " campaigned explicitly on an anti-black , pro-white platform , " while Republicans campaigned on Grant 's popularity and the Union victory in the Civil War
assassination
Assassination of Abraham Lincoln
1868 United States presidential election