Haines continued his private legal practice for fifteen more years before entering public office in 1838, when he was elected to represent Sussex County in the New Jersey Legislative Council by a large majority. Upon his inauguration, he immediately became involved in the Broad Seal War, a bitter partisan controversy over the 1838 elections to the United States Congress. When the House of Representatives seated the Democratic ticket over the Whig claimants, Whig legislators from Morris and Essex counties introduced resolutions denouncing the action; Haines led the Democratic caucus in the ensuing debate. Though the resolutions passed, Haines's leadership role elevated his status within his party and the state.
