The day Time magazine published its report on a photo of Justin Trudeau wearing blackface, discussion exploded online. But less than a week later, online posts about the scandal had all but disappeared, according to new research from McGill University.

In fact, the online discourse around Trudeau's history of wearing blackface dropped off dramatically within three days, according to an analysis of social media posts published today by the Digital Democracy Project, an effort led by the Public Policy Forum and the Max Bell School of Public Policy at McGill University.

"The story breaks and within a couple hours is trending on Twitter, there's a massive amount of coverage," said lead data analyst Aengus Bridgman. "By the next day, it's about half. By the third day, it's about a quarter and it goes down from there to very little discussion by the end of the week."

The findings are based on a dataset of 3 million tweets from the general public from Sept.17 to Sept. 28. A separate dataset of Facebook posts that mention Trudeau and blackface or link to a story covering the issue showed a similar sharp decline in just a few days.

Journalists and politicians on Twitter also followed a similar pattern, with a high amount of tweets about blackface in the first few days that dropped off significantly toward the end of the week.

"We think that the brownface/blackface story offers a pretty unique research moment in an election where an unexpected discourse emerges that nobody could have planned for," said Taylor Owen, the director of the Digital Democracy Project.

The researchers also took a look at accounts that are likely partisan based on the politicians they follow from each party. This showed that, while partisans of all stripes tweeted about the story, it was largely pushed by Conservative supporters.

An analysis of the hashtags used by accounts from these groups, however, show that most likely they were circulating among like-minded people: most of the blackface-related tweets coming from Conservative partisan accounts, for example, were only seen by other Conservative partisans, the report found.

"Among partisan Twitter users, Conservatives are driving the conversation about the controversy," the report found. "The blackface-related hashtags are disproportionately populated by right-leaning partisans who are largely speaking among themselves."