N'afọ 1916, Sandlin bụ onye nnọchiteanya na Democratic National Convention
, nke zutere na St. Louis, Missouri, iji họpụta Onye isi ala US Woodrow Wilson nke New Jersey na osote onye isi ala Thomas R. Marshall nke Indiana, maka okwu nke abụọ ha n'ọfịs. Na 1944, ọ bụ onye ntuli aka onye isi ala maka oge nke anọ nke Franklin Roosevelt.