In the 1860 election, Hamlin was the Republican nominee for Vice President. Selected to run with Abraham Lincoln, who was from Illinois, Hamlin was chosen in part to bring geographic balance to the ticket and in part because as a former Democrat, he could work to convince other anti-slavery Democrats that their future lay with the Republican Party. The Lincoln and Hamlin ticket was successful, and Hamlin served as Vice President from 1861 to 1865, which included all but the last month of the American Civil War. The first Republican Vice President, Hamlin held the office in an era when the office was considered more a part of the legislative branch than the executive; he was not personally close to Lincoln and did not play a major role in his administration. Even so, Hamlin supported the administration's legislative program in his role as presiding officer of the Senate, and he looked for other ways to demonstrate his support for the Union, including a term of service in a Maine militia unit during the war.