At a meeting of local Democrats in Bardstown, Kentucky, in 1859, Brown was nominated to oppose Joshua Jewett for Jewett's seat in the House of Representatives. Despite Brown's protests that he was more than a year younger than the legal age to serve, he was elected over Jewett by about two thousand votes. He did not take his seat until the second congressional session because of his age. He became a member of the Douglas National Committee in 1860 and engaged in a series of debates with supporters of John C. Breckinridge for president, including Breckinridge's cousin, William Campbell Preston Breckinridge.