In 1971, four-term incumbent state representative John Q. Radcliffe resigned to accept a role in the new governor's administration. Robertson ran and was elected in the special election to replace him in the 1971-1972 session of the legislature. He served on the committees on taxation and printing, but lost his bid for re-election in 1972.
In 1979, another opportunity in the legislature presented itself when incumbent state representative Steve Gunderson resigned his seat to accept a role on the staff of congressman Toby Roth. Robertson ran again and defeated former state representative John Q. Radcliffe in the September special election. He ultimately won one more term in the assembly, narrowly defeating Democrat Rodney C. Moen in 1980, before losing re-election in 1982 to Barbara Gronemus after redistricting.
Robertson resumed his law practice, but returned to public service one more time, in 1994, when Governor Tommy Thompson appointed him to the Wisconsin circuit court in Tremplealeau County to fill the vacancy created by the resignation of Judge Richard Galstad. He ran for a full term on the court in April 1995, but was defeated.
Electoral history
Wisconsin Assembly Jackson–Trempealeau District (1971)
Wisconsin Assembly, Jackson–Trempealeau District Special Election, 1971[3]
^Wisconsin Legislative Reference Bureau (1981). "Biographies and pictures". In Theobald, H. Rupert; Robbin, Patricia V. (eds.). The state of Wisconsin 1981-1982 Blue Book (Report). Madison, Wisconsin: State of Wisconsin. p. 83. Retrieved May 17, 2020.
^Wisconsin Legislative Reference Bureau (1971). "Elections in Wisconsin". The state of Wisconsin Blue Book, 1971 (Report). Madison, Wisconsin: State of Wisconsin. pp. 305, 321. Retrieved May 18, 2020.
^Wisconsin Legislative Reference Bureau (1973). "Elections in Wisconsin". In Theobald, H. Rupert; Robbins, Patricia V. (eds.). The state of Wisconsin 1973 Blue Book (Report). Madison, Wisconsin: State of Wisconsin. p. 829. Retrieved May 18, 2020.
^ abWisconsin Legislative Reference Bureau (1981). "Elections in Wisconsin". In Theobald, H. Rupert; Robbins, Patricia V. (eds.). The state of Wisconsin 1981-1982 Blue Book (Report). Madison, Wisconsin: State of Wisconsin. pp. 893, 896, 915, 917. Retrieved May 18, 2020.
^Wisconsin Legislative Reference Bureau (1983). "Elections in Wisconsin". In Theobald, H. Rupert; Robbins, Patricia V. (eds.). The state of Wisconsin 1983-1984 Blue Book (Report). Madison, Wisconsin: State of Wisconsin. pp. 890, 911. Retrieved May 18, 2020.