"So come one, come all," Key told TVNZ. "It's good for politics I reckon."
Holt told the Herald she had always voted Green and became a member earlier this year because of her interest in environmental issues, in particular climate change. The Greens' policies on combating inequality and climate change meant the party was "a natural fit" for her, she said.
Key was "obviously a very good politician", she said, but she felt National was not working hard enough for the environment or for New Zealand's most vulnerable people. She decided to run for Parliament because she "wanted to make a difference herself rather than leave it to other people".
The 36-year-old also believes Parliament needs younger, more interesting MPs.
"I don't want politics to be boring. It looks boring at the moment and we've got some really fresh, exciting faces with the Greens coming through and hopefully we can add some energy into it."
Holt's chances of getting into Parliament will depend on her list placing, which is decided by party members. The Greens have won just one electorate seat in their history and two of the seats Holt is considering, Rodney and Helensville, are safe National seats. Key has held Helensville since 2002 and National's Mark Mitchell won Rodney with a 20,000-vote majority in 2014.
She is not yet sure how many votes her star power could be worth. Another relatively high-profile broadcaster and Dancing With the Stars contestant Tamati Coffey was soundly beaten when he stood for Labour in Rotorua at the last election. He has been selected to run against Te Ururoa Flavell in Waiariki in 2017.
I don't want politics to be boring. It looks boring at the moment and we've got some really fresh, exciting faces with the Greens
coming through ...
"I wouldn't be doing this if I thought it was impossible," Holt said. "It could happen next year. I'm not going to be running away from it if I don't get in."
She admits she has little political experience. But she has been deeply interested in politics all her life. Her grandfather once stood for Social Credit in the Bay of Islands.
She has been volunteering at the party's Kelston office and fronted a Green campaign in Queenstown in September which aimed to raise awareness about climate change by highlighting its impact on the skisports industry.
"My lack of experience is going to hinder me a little bit," she said. "But I am quite a fast learner, and I am quite good at taking these opportunities and running with them."
Holt says she is well aware of the increased scrutiny she will face as a politician. She caused controversy in 2013 when she failed an on-air drugs test while hosting the More FM Breakfast show and two days later was removed from the air after being caught drinking on the job.
"I expect naysayers and people to dredge up old issues," she said. "I have lived a life and I think I've learnt my lessons."