Nicholls was originally a member of the Progressive Conservative (PC) Party before he was removed by Doug Ford in 2021 due to refusing a vaccine.

Nicholls ran in the 2011 Ontario general election as the Progressive Conservative candidate and flipped the riding of Chatham-Kent—Essex from the Liberal Party and remained in position for 11 years.

[8] In 2012, Nicholls called for a more thorough investigation into a massive fish kill incident along the shores of Lake Erie in early September 2012.

In 2015, during a debate about the province's new sexual education curriculum, Nicholls revealed that he does not believe in evolution, and he was not kidding when he said it was "not a bad idea" to stop teaching it in schools.

Nicholls was ejected from the caucus by Premier Doug Ford on August 19, 2021, for vaccine hesitancy, against the policy made by the party.