Continuing our journey back in time to see what the ante-bellum Democratic Governors of Michigan did during the Civil War, today we find:
“Robert McClelland served in the Michigan Constitution Convention of 1835 and was elected to the state legislature in 1837. He became mayor of Monroe in 1841, was elected to the U.S. Congress in 1845, and in 1851 was elected governor of Michigan. He was appointed Secretary of the Interior by President Pierce in 1853. He served for four years.” (Source: Michigan Historic Sites Online)
This doesn’t tell us what he did during the Civil War. The Biographical Dictionary of the United States Congress says after his Interior post he “resumed the practice of law in Detroit, Mich.” and was a “delegate to the Democratic National Conventions in 1848, 1852, and 1868.” So he apparently did not participate in 1860 or 1864. According to the Dictionary of American Biography, Volume XI, Charles Scribner's Sons, New York, 1933, “In 1857 McClelland returned to Michigan, settling down in Detroit to twenty-three years of legal practice. He returned to public service briefly in 1867 as a member of the Michigan constitutional convention. In personality he was always plain and unprepossessing; his manners were somewhat brusque and forbidding; and he was regular and painstaking in his mode of life to an extent which in his later years became proverbial among his neighbors.”
The Elmwood Cemetery website, where he was interred, adds this: “On the eve of the Civil War he advocated moderation and compromise.”
According to the website for distinguished alums of Dickinson College, “McClelland became, among other things, a strong advocate for states' rights, including the right of a state to permit slavery. His star rose in the party and he represented Michigan in several national conventions. He also was an active member of the constitutional convention in Michigan in 1850 and the chair of the state Democratic Convention that year. In 1851, he was elected governor of Michigan and re-elected by an even greater majority in 1852 [defeating Zachariah Chandler]. Soon after, having noted his active part in his presidential election, President Franklin Pierce named him to the cabinet as Secretary of the Interior. In that position, McClelland advised the president to follow his neutral policy concerning Kansas, but most of his recommendations for reform made little progress. Nonetheless, he built a reputation for organization and honesty in a previously chaotic and corrupt department. After James Buchanan's inauguration in 1857, McClelland retired to a long and successful private practice in Detroit. He sat again in a Michigan state constitutional convention in 1867.”
An excellent work by Martin J. Hershock, distinguished history professor at the University of Michigan-Dearborn, entitled The Paradox of Progress about the 1837-1878 period in Michigan, says McClleland blamed Republicans for creating the secession crisis in late 1860 (p. 162) and in turn was accused of disloyalty (p. 169). McClelland battled abolitionism (p. 170), criticized the conduct of the war (p. 171), and lamented the Emancipation Proclamation.
Without more research, the conclusion seems to be that he then laid rather low during the rest of the conflict. But the online summary of his papers at the Bentley Historical Library holds a hint: "The collection includes Latin salutatory for the opening of Dickinson College, 1829, biographical sketch, letter, 1861, to Augusta McClelland affirming his strong loyalty to the Union, two notebooks containing campaign speeches and notes on the Civil War”. Those documents might shed light on the matter and help make a more complete assessment.