When President Trump announced early Friday that he and the first lady had tested positive for COVID-19, it was just one in a series of head-spinning shocks in an already tumultuous campaign.
This past Tuesday a ferocious debate left many viewers stunned.
That came on the heels of the passing of Justice Ruth Bader Ginsburg, and the lightning-quick nomination of conservative Judge Amy Coney Barrett to replace her.
There's a name for unexpected events that occur late in presidential campaigns and have the potential to change the course of the election – they're called "October Surprises."
This year they got an early start – all but the president's positive COVID test happened in September.
"It's our October Surprise early," said Margaret Carlson, who has covered many presidential campaigns for Time Magazine. She said some October Surprises are carefully orchestrated, but others come out of the blue.
"Is it a man-made or woman-made surprise?" Carlson said. "Or is it an event beyond anyone's capacity to control, you know? A hurricane, the financial markets collapsing in 2008? Or is it something in an ongoing scandal?"
The term "October Surprise" first appeared in our political lexicon in 1980 when Republican Ronald Reagan was running against Democratic President Jimmy Carter.
Fifty-two Americans were being held hostage in Iran during an election year, and there was no end in sight.
"In 1980, Jimmy Carter and his staff really believed that if they could show progress in freeing the hostages, that would be enough; that would take him over," said Larry Sabato, director of the University of Virginia Center for Politics. "What they didn't count on was that the promises from the Iranians completely collapsed on the Sunday before the Tuesday election. So basically, Americans were told right before they went to the polls that it was either hopeless or they'd better try somebody new who would try new things to get the hostages back."
"So, that was an October Surprise that Jimmy Carter thought was going to help him, but it reversed itself?" asked CBS News national correspondent Chip Reid.
"It helped Reagan instead," Sabato replied.
1980 might have been when the term "October Surprise" was coined, but Sabato said the first president to benefit decisively from a last-minute turn of events was Abraham Lincoln: "Even Lincoln had, not an October Surprise, but a September Surprise, when Sherman took Atlanta. It probably saved Lincoln's second term. He himself thought that he was going to lose, and most of his cabinet did. And it built enthusiasm in the North. And finally they could see the light at the end of the tunnel."
That light was a resounding Lincoln victory.
And while it's rare that an October Surprise actually changes the outcome of an election, Washington Post reporter Devlin Barrett believes it did happen four years ago.
"Yeah, I think Jim Comey, the director of the FBI, without intending to, changed the outcome of the election," Barrett said.
Barrett is the author of a just-released book, "October Surprise: How the FBI Tried to Save Itself and Crashed an Election" (PublicAffairs), in which he contends that the key 2016 October Surprise came in the form of a letter to Congress from then-Director of the FBI James Comey.
The letter announced a new FBI investigation into emails found on a laptop belonging to Clinton campaign advisor Huma Abedin, whose husband, former New York Congressman Anthony Weiner, was under investigation for online sex crimes.
The announcement was made just 11 days before the election.
Reid asked, "One reason it was so powerful is because Trump had made such a big deal out of the Hillary Clinton emails, so this fit right into one of his main messages against her?"
"That's absolutely right," Barrett replied. "It absolutely fit into the Republican critique and attack on Hillary Clinton. But the other part of it, too, was that it came from a very credible place."
"If FBI Director Comey had not sent this letter to Capitol Hill, you believe Hillary Clinton would be president today?" asked Reid.
"I do, and more importantly the people who study the data believe it, and what they say is it is the single most measureable impact on the outcome."
Barrett admitted we can never know with absolute certainty that it did change the election result, but we do know that another 2016 October Surprise did not.
"And when you're a star, they let you do it. You can do anything. ... Grab 'em by the p***y. You can do anything."
The notorious "Access Hollywood" tape of Mr. Trump bragging, in 2005, about sexually accosting women did not block his path to victory.
Larry Sabato said it's unlikely an October Surprise this year will change the result of the election: "I don't think October Surprises are gonna work as well this year, because we're so polarized. Everybody's in their own tribe, Democratic or Republican. And they're not going to move."
Maybe so, but with the way things are going, more October – and even November – Surprises seem likely, in a campaign that makes the term "political rollercoaster" sound quaint.