Howe entered publicly into the antislavery struggle for the first time in 1846 when, as a "Conscience Whig", he was an unsuccessful candidate for Congress against Robert C. Winthrop. Howe was one of the founders of an antislavery newspaper, the Boston "Daily Commonwealth", which he edited (1851–1853) with the assistance of his wife Julia Ward Howe. He was a prominent member of the Kansas Committee in Massachusetts.