baker was outspokenly anti-slavery, and following the break-up of the whig party, he joined the newly formed republican party in 1854. at the state convention in 1856, he was nominated to run as lieutenant governor on the ticket with oliver morton a governor. the election was one of the most divisive in state history, with both sides making scathing attacks on the other. despite the party's merger with several other third parties, the republicans lost the election and baker returned to his law practice in evansville.