Rep. Diane Black, R-Tenn., on Thursday night lost the GOP gubernatorial primary in a major upset to conservative political outsider and constructions executive Bill Lee.

Black, the former chairman of the Budget Committee, had the endorsement of Vice President Mike Pence, and was favored to win in a crowded candidate field, especially above Lee, who as recently as last month was down double digits in the polls.

President Trump has a 56 percent approval rating in Tennessee, but support from his administration failed to secure Black's victory in the red state.

Former state economic development chief Randy Boyd was considered Black's primary rival, and had the backing of former Arkansas Gov. Mike Huckabee.

Lee spent $5 million of his own funds during his campaign, according to MarketWatch , and took advantage of the political sparring between Black and Boyd to focus on traveling the state to tout his conservative Christian values.

The 57-year-old businessman’s poll numbers surged in the last week of his campaign.

The night before the primary vote, supporters of Black’s campaign realized the threat posed by Lee and released an advertisement claiming Lee’s company fired an employee for being deployed by the Army National Guard.

Lee denies the allegations.