Lucinda Rex, right, and Clarity Thorne embrace during a candlelight vigil on June 13 for the victims of a mass shooting at the Pulse nightclub in Orlando. (David Goldman/AP)

Nobody knows what issues will decide the 2016 election, because nobody knows what will happen over the next four and a half months. The things people care and talk about may depend heavily on world and domestic events that nobody can predict.

That's the conceit of the "October Surprise." For the uninitiated, that's the thing that could happen just before an election that totally changes how people think about the race and has the potential to raise the fortunes of one candidate and sink another.

The mass shooting in Orlando early Sunday morning was certainly one of those kinds of events. It didn't happen in October, of course, but it instantly changed the political priorities of the American public in a big way. Suddenly, the issues of terrorism, radical Islam, gun rights and LGBT rights are things politicians are compelled to talk about — because that's what interests people in the aftermath of tragedy.

But just how rapidly does that issue matrix shift? The charts below, which are based on data from the Massachusetts Institute of Technology's Media Lab's Laboratory for Social Machines, offer some clues.

While terrorism, guns and LGBT issues were about 10 percent of the election-related conversation on Twitter for most of the month of June, after Sunday, all of them jumped up. By Sunday, Monday and Tuesday, more than half of the conversations comprised these issues, each surpassing a topic that simmered in the weeks before: immigration (probably due to Donald Trump's controversial comments about a judge of Mexican descent).


 

Guns were a popular issue across the board — probably both for those pushing for new laws and those resisting such calls. But as the charts below show, they were more a topic of conversation for Twitter users who follow Hillary Clinton than follow Donald Trump.

This is probably because Democrats, as we wrote Friday, are more likely to view the Orlando tragedy as an example of domestic gun violence than an example of Islamic terrorism.


 

Republicans, meanwhile, view the tragedy in a much-different light — which could be why Trump followers were less likely to talk about guns and LGBT issues and more likely to talk about terrorism.


 

Special thanks to data scientists Soroush Vosoughi and Prashanth Vijayaraghaven at MIT's Laboratory for Social Machines for this analysis.