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. He 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. With Franklin Benjamin Sanborn, George Luther Stearns, Theodore Parker, and Gerrit Smith, he was interested in the plans of John Brown. Although he disapproved of the attack upon Harper's Ferry, Howe had funded John Brown's work as a member of the Secret Six. After Brown's arrest, Howe temporarily fled to Canada to escape prosecution.