His brief term as governor was marked by the calling of a state constitutional convention and overshadowed by the national anti-slavery debate, where Dunning urged state leaders to issue and forward resolutions to Congress expressing opposition to the expansion of slavery.

After the death of his father, he, his mother, and one older brother moved to Bloomington, Indiana, where Dunning briefly taught school.

He returned to his mother and older brother in Bloomington and began to study law in the office of future Governor James Whitcomb and Congressman Tilghman A. Howard before being admitted to the bar in 1833.

During his years in the Indiana General Assembly, he had voted for the Mammoth Internal Improvement Act that had led the state to bankruptcy in 1841.

Indiana had just emerged from a period of bankruptcy, and Dunning oversaw the final phase of the process, ensuring the public works were turned over to the state's creditors and that the debt reduction deal was fully carried out.

Congress was debating the extension of slavery in the western territories during his term, leading to bitter hostilities between northern and southern leaders.

Dunning delivered a speech to the General Assembly in which he condemned the expansion of slavery and called for its gradual elimination.

He was the first outspoken anti-slavery governor since William Hendricks, and he recommended the assembly pass a resolution for him to forward to Congress.

In response, the assembly passed a strong resolution requesting Indiana's congressional delegation to oppose the expansion of slavery.

Among his proposals was a ban on special legislation, because the legislature had become notorious for passing laws that were only applied to certain counties or towns.

Dunning was able to have a clause entered into article 4 of the constitution that required all laws passed by the assembly to be applied uniformly across the entire state, ending the practice.

[5] In 1861, he left the Democratic party, and was reelected to the state senate as an Independent and supported the Republican governor throughout the war.