[6] He held this post until 1838, when he moved to Washington, D.C. to accept a position in the Department of the Treasury while Levi Woodbury of New Hampshire was serving as Secretary.

[11] A member of the Democratic Party for most of his career, Metcalf later became recognized as anti-slavery and an opponent of Franklin Pierce's attempts to obtain passage of the Kansas–Nebraska Act.

[12] As a result of Metcalf's opposition to slavery, in 1855 he was nominated for Governor by the Know Nothing movement, which increasingly incorporated anti-slavery sentiment into its core Nativism in New England states.

This effort was promoted by Free Soil Democrats including John P. Hale, who hoped to create a movement that would send New Hampshire anti-slavery activists to the United States Senate and help build the nascent Republican Party.

)[14] Metcalf won the 1855 race for Governor, defeating incumbent Nathaniel B. Baker, James Bell and Asa Fowler.