[7] Rennick, a member of the National Right faction of the Liberal Party,[8] was a Senate candidate for the LNP at the 2016 federal election, but failed to win a seat.

The LNP rejected as "offensive and ridiculous" any suggestion the donations played a role in his pre-selection, and highlighted the fact that some of their members self-funded their elections.

[9] In an interview on Sky News Australia in 2020, Rennick spoke about government overreach in the "classroom and the bedroom" and compared it to a communist takeover by the bureaucracy.

[15] He has been viewed as a "right wing climate denialist",[15] and was singled out by the ALP leader Anthony Albanese as someone "who thinks the Bureau of Meteorology is part of global conspiracy".

While The Guardian did not disclose what the posts said, it described them as "casting doubt over the accuracy of PCR tests", and said that Rennick "questioned why Australia's Therapeutic Goods Administration (TGA) had not yet recommended use of ivermectin".

[24] In November 2021, Rennick was one of five Liberal-aligned senators who voted against the government in support of the COVID-19 Vaccination Status (Prevention of Discrimination) Bill 2021, sponsored by One Nation.

The Chief Medical Officer of Australia, Dr Paul Kelly, said that the Pfizer vaccine is “worthwhile, safe and effective” for children aged five to 11.

The Australian Medical Association vice-president, Chris Moy, told The Guardian that Rennick’s surveys of adverse events were “as far away from science as possible” because they “force one answer he wants”.

[7] He called Labor's policy of providing free childcare to all three-year-olds in Australia a conspiracy "to strengthen the role the state has in raising a child at the expense of parents".

[32] Rennick's position is that "subject to financial considerations, if we can leave children at home with at least one parent, that's something worth striving for", but he suggested that "early childhood education is ... not the best way to invest in our future".

[33] In September 2018 Rennick advocated closer ties with Russia because "they're part of the West; they drink, they're Christians, they play soccer, they're Caucasian".