During the late 1960s and early 1970s, he became prominent in the Progressive Youth Movement, a radical left-wing organisation, and was arrested 33 times during political protests.

[5] He famously celebrated, much to some people's disgust, by towing his concrete mixer (named "Karl Marx"[6]) behind the mayoral Daimler in the 1983 Henderson Christmas parade.

[7][8] Shadbolt's election represented the deep cynicism that many voters had felt about the Waitemata City Council, which was known for in-fighting.

[5] This triggered an audit by the central government, which found evidence of cronyism and improper management of funds, however not as wide-spread as alleged by Taylor.

In October 2002, Shadbolt told a conference of New Zealand's Disabled Persons Assembly that Invercargill had "an innovative approach to public transport, currently centred on 'Freebie the Bus' travelling the 'Purple Circle'".

"In the past I've had either no contenders, but this time I had a television producer and a sitting councillor who had also been an investigative journalist, so it was pretty tough opposition.

Shadbolt had drawn criticism from fellow councillors for using Invercargill City Council (ICC) properties to store his personal belongings.

In response, Shadbolt alleged that he was the victim of workplace bullying and criticised the leaking of a mayoral email to the media.

[22][23] An informal survey conducted by the Otago Daily Times found that 82% of respondents (157 individuals) believed that Shadbolt should resign as Mayor of Invercargill.

[23] In mid-July 2022, Shadbolt was involved in a dispute with Deputy Mayor Clark over whether the Council should cover his rental car expenses when attending a Local Government New Zealand conference in Palmerston North.

Shadbolt argued that he was entitled to financial support from the ICC since he was representing Invercargill ratepayers in his capacity as Mayor.

[30] In June 2015, the Invercargill City councillor Karen Arnold filed a defamation case against Shadbolt and Stuff media company (then known as Fairfax New Zealand) at the Wellington High Court, alleging that Shadbolt had defamed her in four columns published in the Fairfax–owned Southland Times newspaper between October 2014 and April 2015.

[31][32] Shadbolt and Arnold had clashed about the Invercargill City Council's holding company Holdco borrowing an extra NZ$130 million but then declining to invest in a kākāpō centre.

In March 2020, Shadbolt tried to get the Invercargill City Council to cover $448,000 worth of expenses incurred during his defamation trial under an indemnity clause in the Local Government Act.

[34] By late September 2020, Newshub reported that Shadbolt was facing bankruptcy, owing over NZ$350,000 in legal fees.

In the 1990s he appeared in an advertisement promoting New Zealand cheese, where he humorously repeated the phrase "I don't care where as long as I'm mayor", referencing his dual mayoralties.

[3] He also played in the movie The World's Fastest Indian, portraying a good friend of Burt Munro who organised social events for Invercargill's motorcycling community.

[1][45] Shadbolt was hospitalised for two weeks in April 2006 after rolling the mayoral car near Winton while returning from a work trip to Queenstown.

He was charged with careless driving and could have faced a maximum fine of $3000, however he was instead discharged and ordered to pay $300 each to St John New Zealand and the Winton volunteer fire brigade.