Since Australians began ticking boxes in the same-sex marriage postal plebiscite, the ‘yes' vote has been regularly touted as a clear winner.

It had an air of inevitability, like Winx winning a third straight Cox Plate.

But suddenly, a group of academics at Griffith University have bucked the trend.

Analysing Twitter opinion, they have come to the conclusion that in fact, the ‘no' vote will edge ahead in a tight finish.

One of the problems with predicting poll outcomes is that people are often reluctant to say out loud what they really think about issues

David Tuffley and Bela Stantic used the same advanced data analysis techniques that correctly predicted Donald Trump's presidential election win in 2016.

And from studying more than 458,000 tweets, they believe the ‘yes' voters will only make up 49% of the returned ballots when the poll closes on November 7.

While 72% of tweets favoured same-sex marriage, less than 15% were sent by people over the age of 55, the Griffith University study shows.

Then, when the pair took the sentiment of unique users into account, the adjusted ‘yes' vote figure went from 72 to 57%.

Finally, when they took into account the low proportion of tweets from people over 55, and matched it against the 36% of the voter pool they represent, the support for ‘yes' dropped to 49%.

The pair said a major factor behind their predicted swing was the constraints of political correctness.

“So it is likely to be a close-run result, much closer than the earlier polls suggested, and leaning in the direction of ‘no',” Professor Stantic and Mr Tuffley said.

“One of the problems with predicting poll outcomes is that people are often reluctant to say out loud what they really think about issues.

“What people say online can often be more accurate than what they say to each other in this age of political correctness.”