in 1856, dayton was selected by the nascent republican party as their first nominee for vice president of the united states over abraham lincoln at the philadelphia convention. he and his running mate, john c. fremont, lost to the democratic ticket of james buchanan and john c. breckinridge. afterwards, he served as new jersey attorney general until 1861, when president lincoln appointed him minister to france. he served from may 1861 until his death in december 1864. his service spanned most of the american civil war.