The Equality Campaign says the text messages it blasted out across Australia over the weekend drove 170,000 people to click through and seek information on the same-sex marriage postal survey.
According to the "yes" camp, another 20,000 signed up to volunteer as a result of the weekend campaign, which some recipients and critics - including Australian Christian Lobby managing director Lyle Shelton - have argued was an invasion of privacy.
Responding to concerns, the Australian Communications and Media Authority said on Monday that the sending of unsolicited calls, emails or SMS messages like this does not break any laws if it is not promoting or selling a product or service.
"Communications about political matters do not usually include a commercial element," the ACMA said, absolving the Equality Campaign of any breach under the Do Not Call Register Act or the Spam Act.
The "yes" campaign said it had sought legal advice to make sure the messages were allowed and also pointed to the previous examples of organisations - generally political parties in the lead up to elections - deploying the tactic.
During last year's election campaign, a message organised by Queensland Labor - but notoriously appearing as if it was from Medicare - peppered the country. In that same campaign, many voters would have received a message from "MTurnbull" urging them to "see it through" and vote Liberal.
"We need to do everything we can to ensure we can get this done and move forward. And we are grateful to all those who volunteered and pledged to vote yes as a result of the SMS," Equality Campaign co-chair Alex Greenwich said.
Labor was dismissive of concerns over the "yes" messages, with deputy leader Tanya Plibersek labelling the critics "irritating". The Equality Campaign said it would use whatever tools it could to achieve a "yes" result.
But the example has triggered broader concerns over privacy, with some voters questioning how unlisted phone numbers seemingly came into the possession of an organisation they had never interacted with.
Fairfax Media understands the Equality Campaign's text messages were sent out by a provider that randomly generates a vast trove of possible Australian phone numbers. This means the tactic is also not affected by the Privacy Act, which regulates the handling of people's personal information. It also has broad exemptions for political activities.
Another common process, not used in this case, is where organisations purchase databases of phone numbers generally compiled when customers sign up with businesses and, under the terms and conditions, grant permission for their contact details to be shared.
"There are marketing database companies both in Australia and globally who specialise in acquiring, managing and delivering to electronic addresses," said Patrick Fair, a lawyer at Baker McKenzie specialising in telecommunications and privacy.
"It's not like this stuff falls from the sky," the person said.