On Saturday evening, when the New York Times released its explosive report that Donald Trump had claimed a $915 million loss on his 1995 taxes and possibly hadn’t paid federal taxes in the 18 years that followed, it was a clear sign that the election had entered a new phase. Though the revelation itself was astounding, the timing was anything but: Less than a day into the new month, 2016’s first “October surprise” had arrived. 

Political history is littered with the charred remains of such late-in the-election bombshells that scramble political calculus just as the stakes are at their highest. An “October surprise” can be happenstance or deliberately orchestrated; international (e.g. the outbreak of war) or domestic (e.g. a massive economic rally). Sometimes it’s personal, with a long-hidden skeleton spilling out from a candidate’s closet. It can save a political campaign as quickly as it can wreck one. And occasionally, it can even decide an election and set the course of the nation.

With four weeks left in the October and one surprise down already, it’s quite possible that there will be shockers yet to come—with Russian hackers, Donald Trump’s penchant for controversy, Julian Assange on the prowl, Hillary Clinton’s missing emails and a precarious scenario in the Middle East, it is anyone’s guess.