However, both questioned their rival's suitability to the position.
At a press conference in Invercargill yesterday, Ms Prentice (51) announced she would stand for the mayoralty and "to afford the position of mayor the dignity which it deserves".
"I have thought long and hard about standing and keep finding myself concerned for the future of our city, its residents and its ratepayers."
Mr Shadbolt's failed attempt to dump long-serving deputy mayor, Neil Boniface, coupled with "tremendous support" from the public helped persuade her to stand for the position.
Other election issues include: Mr Shadbolt's (63) use of a mayoral credit card, trips overseas, population growth, refuse, and healing what appeared to be a divided council.
The 51-year-old said she was a proud Southlander who chose to stay in Invercargill despite people telling her she would need to move to advance her singing career.
"My heart and home are in this city."
The hardest part of making her decision to stand would be ceasing her duties with the Invercargill Licensing Trust, which over the past six years had provided her with her only political experience.
Asked if she could win what is likely to be a high-profile contest against the seasoned political campaigner, Ms Prentice was diplomatic: "That is for the public to decide".
If unsuccessful, Ms Prentice said she would remain in the city, but was unsure if Mr Shadbolt, who once coined the phrase `I don't care where as long as I am mayor', would do the same.
However, Mr Shadbolt told the Otago Daily Times the city was "home now" and, if he lost the election, he would remain in the city to write the great New Zealand novel.
"Then I would be back in three years to have another crack."
Mr Shadbolt, who first served as Invercargill Mayor from 1993-95 and since 1998, conceded he had had "a good run in Invercargill" and was not ready to hand over the mayoral chains.
While Ms Prentice was the highest profile candidate to challenge him, her political inexperience had already shown itself by her announcing her intentions six months out from the local body elections.
"She will have all this publicity, but you can't sustain it."
Her role as vice-president of the Invercargill Licensing Trust was akin to a "Santa Claus position" and as a result of the millions in grants at their disposal members became very popular, he said.
"Once they become a tax collector, that is a different story."
While politically, Ms Prentice was something of an "unknown quantity", the high-profile campaign would result in a bigger election turnout and this had to be good for the city, he said.
