After delivering a rousing commencement address at Oberlin College in 1839, the school offered Blanchard a professorship, but he declined. In 1841, Blanchard founded the "Presbyterian of the West", later known as the "Herald and Presbyter", a radical Presbyterian weekly journal. He represented the Ohio State Anti-Slavery Society as a delegate to the 1843 World Anti-Slavery Convention in London, England and was elected its American vice president. In early October 1845, in Cincinnati, Ohio, Blanchard debated the morality of slavery with fellow Presbyterian minister Nathan Lewis Rice (December 29, 1807 - June 11, 1877). This debate was recorded in full, and later published as "A Debate on Slavery Held in the City of Cincinnati" (Cincinnati: William H. Moore & Co., 1846). Blanchard's first opposition to Freemasonry came in 1845, when he condemned a Covington, Kentucky lodge that refused aid to a widow of a long-time member. A mob of over fifty men attacked him over the article. The next Sunday, Blanchard preached against secret societies, a position that he would hold for the rest of his life.