Wyoming Governor Matt Mead (R) appointed Buchanan to serve as Wyoming secretary of state on March 1, 2018. He succeeded former officeholder Ed Murray, who resigned in February 2018 amid sexual misconduct allegations. Buchanan was sworn into office on March 5, 2018. He served for the remainder of Murray's term, which expired in January 2019. Buchanan was elected to a full term in 2018.

Wyoming Governor Matt Mead (R) appointed Buchanan to serve as Wyoming secretary of state on March 1, 2018. He succeeded former officeholder Ed Murray, who resigned in February 2018 amid sexual misconduct allegations. Buchanan was sworn into office on March 5, 2018. He served for the remainder of Murray's term, which expired in January 2019. Buchanan was elected to a full term in 2018.

Buchanan resigned from office on September 16, 2022.

Buchanan represented District 4 in the Wyoming House of Representatives from 2003 to 2013. He served as House majority whip from 2007 to 2008, House majority floor leader from 2009 to 2011, and speaker of the House, from 2011 to 2013.