Rublee began his political and journalism career in 1852, when he moved back to Madison. He was legislative reporter for the Madison Argus and Democrat in 1852–53. In 1853 he started work at the Wisconsin State Journal, and in 1854 purchased a part interest in the paper. He was secretary of the state mass meeting held at Madison on July 13, 1854, which formed the state chapter of the Republican party. The party had been started in embryonic form in March in Ripon, but this mass meeting was the first serious establishment of the party as a lasting organized political force. He was Republican party chair 1859–1869, and in 1868 a delegate to the national Republican convention. From 1856 to 1858 he was Wisconsin State Librarian. From 1857 to 1871 he was a curator of State Historical Society of Wisconsin, serving with such notable nineteenth-century Wisconsin figures as James Duane Doty, Cyrus Woodman and Lyman Draper. He married Katherine Hopkins in 1857.
