I had said at least two times this week that “game changers” rarely happen. Single events or revelations rarely upend presidential elections, which tend to be decided by more structural forces instead, such as political partisanship and the state of the economy. And then, on Friday, the Washington Post’s David Fahrenthold revealed a video recording of Donald Trump making crude and vulgar comments about women — and the way rich men can treat them. The response to the Trump tape suggests that we might be seeing a real change in the political landscape. “Game change” moments are few and far between, and Hillary Clinton was already leading Trump pretty comfortably in national and swing state polls. But what might make the Trump tape have more of an impact than previous Trump controversies?

The content

This is the most obvious possibility. Many commentators have hastened to point out that the remarks were not just “lewd” or suggestive — they advocated sexual assault. The recording shows Trump doing several things presidential candidates aren’t supposed to do: treat fellow humans like they’re objects, talk about doing something illegal, encouraging others to break the law.

Relying on the content as an explanation is challenging in this election, though. Trump’s willingness to insult women was apparent at the first primary debate in August 2015 and has been evident on many occasions since then. What one voter called “volatility” is also part of Trump’s political persona. Writing about what makes political scandals stick in 2008, my colleague Nate Silver pointed out that the most potent scandals reinforce a “core negative perception about the candidate, particularly one that had henceforth been difficult to articulate” — but not a perception that’s already received so much coverage that “little further damage can be done.” The implication is somewhat counterintuitive: “Game change” moments are not surprising; rather, they confirm what we already suspected or even pretty much knew, but in ways that have new implications for the campaign. John McCain’s selection of Sarah Palin as his running mate in 2008 fits this model — there were doubts about McCain’s judgment, and then he selected a running mate who wasn’t well prepared or vetted. Trump’s comments in the video reveal a willingness to violate social norms — and fellow human beings — that goes beyond what the candidate has said before. But given the apparently flimsy role of norms this year, will this be enough to change the trajectory of the election?

Timing and context

Much of the literature on campaign effects in U.S. presidential elections points to two findings. First, the main role of campaigns is what political scientists call “partisan activation.” This means that media coverage, candidate speeches, debates and advertising help voters identify the candidate who matches their preferences on the issues — the campaign doesn’t persuade people to switch political sides so much as make clear which candidate is already on their side. The second contribution is about timing: Partisan activation happens over the course of the campaign, so by October, voters start to make up their minds, with less potential for major shifts in support.

One of the things that’s been most remarkable about this campaign is that despite the unconventional Republican nominee, these familiar dynamics have been evident. Partisan activation has so far worked reasonably well for Trump, with initially reluctant Republican voters, reminded of their disagreements with Clinton, declaring their intent to vote for the party nominee.

Where does Friday’s revelation fit into this? It’s early October, with both conventions down and two debates in the books with two to go. Much of the partisan activation that’s going to happen has already happened. Still, for the campaigns and lower-information voters, who may be just tuning in, this is an intense time. And for high-information voters, political journalists and other people who have been paying attention to the campaign for a long time, we’re at the point where it’s become a bit of a slog. Anything resembling a real campaign development is unexpected and welcome for this second group. This could prove a potent combination. It offers a new and salacious story just as the final stage of the campaign ramps up.

Party factors

The typical “game change” narrative usually describes an interaction among media, candidates and voters. But if the Trump tape proves to change the course of the election, it will probably be a party story. Elected Republicans have largely hopped aboard the Trump bandwagon, but many prominent officials did so reluctantly. House Speaker Paul Ryan and Republican National Committee Chairman Reince Priebus, for example, endorsed Trump only after several meetings. Ryan was supposed to appear with Trump for the first time at a campaign event this weekend in Wisconsin. That’s not happening anymore. Ryan and Priebus have condemned Trump’s comments.

Historically — though we don’t have a lot of instances to draw from — politicians are really in trouble when their parties turn on them. Losing support from his own party was part of what led to President Richard Nixon’s resignation as the Watergate scandal worsened. In contrast, Democrats generally stuck with Bill Clinton during his impeachment hearing in the late 1990s. What was the difference between these two situations? A combination of conscience and political calculation, as usual, shaped politicians’ response. Republican and Democratic legislators alike received constituent mail about Watergate, mostly urging Nixon’s removal. Clinton, in contrast, remained fairly popular with the public through his impeachment proceedings.

Just as Republican members of Congress abandoned Nixon and called for his resignation, a few top Republicans have withdrawn their support for the 2016 ticket, including Utah Rep. Jason Chaffetz. Several of these officials have also called for Trump to leave the race. New Hampshire Sen. Kelly Ayotte has announced her intention to write in Mike Pence when she votes in November. But at the time of this writing, major party leaders had not withdrawn their endorsements.

Of course, this isn’t Watergate, and Trump isn’t a sitting president. If Trump bows out, Gerald Ford won’t become president, Hillary Clinton (most likely) will. That undoubtedly changes the messages Republican leaders will hear from their constituents — and their own sense of the right thing to do. FiveThirtyEight contributor Daniel Nichanian is keeping a list of Republican positions on Trump, and so far the balance is toward denouncing the remarks but not withdrawing support. Whether that remains the course most GOP officials take or whether there’s a more wholesale abandonment of Trump will go a long way toward determining how much of an effect the Trump tape has on the race. After Trump won the nomination, there was some noise about focusing on the down-ballot races and pulling back from the presidential contest, and maybe that’s what will happen now.

Nevertheless, when the game is this partisan, it resists change. Because the election is close and the nominee is already controversial — more than 50 percent of the Republican primary electorate voted for someone else — GOP leaders could make a big difference in Trump’s electoral support. Signals from people like Ryan and other elected Republicans play a role in partisan activation. But for precisely this reason, they may choose not to pull the plug on him entirely.