Supporters of an Indigenous Voice to parliament say the cause is far from lost as internal polling shows the No vote is softer than the Yes vote, and about a quarter of voters are undecided and could be wooed by a short, sharp campaign.

Third-party polling seen by The Australian Financial Review, as well as research conducted separately by federal Labor and the Yes23 Campaign, all come to the same conclusion that the outcome of the referendum was, a source said, “still very much up for grabs”.