Kammala jumla mai zuwa: Da farko dan Democrat mai 'yanci, Underwood ya zama dan Republican lokacin da aka shirya jam'iyyar kuma ya zama Shugaban taron Jam'iyyar Republican na farko na jihar Vermont a 1856. Ya kuma yi aiki a matsayin wakili ga na farko
Taron kasa na Jamhuriyar Republican daga baya a wannan shekarar.