Trauner ran unsuccessfully on questioning Trump's policies but got little support in his bid to become Wyoming's first Democrat in the Senate in over 40 years.
Gordon's election marks the first time Wyoming's governor's office changes hands without changing parties since Democrat Mike Sullivan's election in 1986.
By many measures, times have been tough in Wyoming since 2014, when oil drilling all but ground to a halt amid weak markets for natural gas and thermal coal.