Groesbeck's entrance into state politics came in 1912 he led efforts to select a delegation to the
Republican National Convention favoring the renomination of
President William Howard Taft. Groesbeck also actively led the party faction supporting Taft in the
general election. That same year, Groesbeck was elected the
state party chairman, serving until 1914. In 1916, Groesbeck was elected
attorney general of Michigan, and was re-elected in 1918. As reported in
The New York Times, Attorney General Groesbeck supported a call for
Henry Ford to run for the
United States Senate as a
Republican. This vision drew opposition from many other Republicans. In 1920, he won the Republican primary election for governor and defeated Democrat and former governor
Woodbridge N. Ferris in the
general election. After being re-elected in 1922 and 1924, Groesbeck lost to
Fred W. Green in the 1926 Republican primary election. In 1925, Groesbeck vetoed legislation that would have created a
state poet laureate.
Time magazine reported: Forgetful of the state poets of republican Athens, the Governor's historical knowledge led him to describe the bill as "a reversion to monarchical customs" which "has no place in a republican form of government." During his six years in office, the state's highway growth continued, prison reform measures were sanctioned, state titles for automobiles began, and state government was restructured and consolidated. He was defeated in the 1930 Republican primary election by
Wilber M. Brucker. ==Retirement, death and legacy==