Benjamin was a supporter of the Whig Party from the time of its formation in the early 1830s. He became increasingly involved in the party, and in 1841 ran unsuccessfully for the New Orleans Board of Aldermen. The following year, he was nominated for the Louisiana House of Representatives. He was elected, though the Democrats alleged fraud: Whig supporters, to obtain the vote at a time when the state had a restrictive property qualification for suffrage, acquired licenses for carriages. A voter did not have to demonstrate that the carriage existed, but his license had to be accepted as evidence of ownership by election officials. The Democratic press blamed Benjamin as the strategist behind this maneuver. In 1844, the legislature voted to hold a constitutional convention, and Benjamin was chosen as a delegate from New Orleans. At the convention, Benjamin successfully opposed counting a slave as three-fifths of a human being for purposes of representation in state elections, as was done in federal elections. His position prevailed, and slaves were not counted at all for electoral purposes in Louisiana state elections. According to Evans, his "tact, courtesy, and ability to find compromises impressed the political elders in all corners of the state".