Kennett was elected as an Opposition Party candidate to the 34th Congress (March 4, 1855 – March 3, 1857).
After losing his re-election, he retired to his home near St. Louis Missouri.
He later moved to Europe in 1867, where he remained until his death in Paris, France, on April 12, 1873.
He was interred in Bellefontaine Cemetery, St. Louis, Missouri.