A political commentator says Judith Collins isn't off the hook yet over the Andrew Falloon scandal.

The Rangitata MP has resigned, after a pornographic image was sent from his phone to a young female university student.

He claims someone else sent it, while he left his phone unattended at a party.

In a statement, Collins has said Falloon is facing significant mental health issues.

Commentator Brigitte Morten told Kate Hawkesby Collins doesn't want to personally attach herself to this story.

“If she had done more media yesterday afternoon there is no doubt that would’ve occurred. But as soon as she does do media, she will be pulled up on it.”

Morten says it's happened quite fast, and very close to the election.

"There will be questions around pay, whether Falloon gets paid until the election and even for a few months afterwards. But whatever happens, we won't see him around Parliament again."

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