The ACT Party is predicting Prime Minister John Key will change his mind over his decision to rule out the 'Red Peak' flag design in the final options.
Public support is building, with an online petition nudging 30,000 signatures this morning.
ACT leader David Seymour says the Prime Minister's changed his mind on taking in more refugees, and he'll do it again with the flag.
"When public opinion gets behind something, we have a Prime Minister that listens, a Prime Minister that wants the flag project to succeed and he's finally seeing some of the enthusiasm that we've all been waiting for."
Mr Seymour says he won't try introducing his own Bill to Parliament forcing the change because he fears Key would vote it down.
Mr Key yesterday said it would take a change in the law to introduce the Red Peak flag as a fifth option, but Mr Seymour and legal experts say it would only take an order in council to replace one of the designs, leaving the total number of options at four.