He served as the sixth Governor of Texas for one term but notably was the only person to ever defeat Sam Houston in a political contest.

[1][3] During his time in the legislature and as Lieutenant Governor, he gained a reputation as a loyal member of the Democratic Party and an advocate for states' rights.

[1][2] Sam Houston had upset many voters with his pro-Union position, association with the Know Nothings during 1855, and his vote against the Kansas–Nebraska Act.

[1] During Runnels' administration, primary concerns were the slavery issue and safety of settlers in the western frontier.

[1] On the issue of frontier security, the governor commissioned Colonel John "Rip" Ford as senior captain of the Texas Rangers on January 27, 1858.

Later in the year, the Rangers fought an inconclusive battle in the Rio Grande Valley against Mexican bandit Juan Cortina.