To work as someone who covers Donald Trump for a living is to sometimes doubt your own memory. Quite often, a story that everyone else treats as a new and stunning revelation seems to you like something you’ve heard before.

To take one example: Last July, there was a modest uproar after Trump gave a speech in North Carolina in which he offered tempered praise for former Iraqi dictator Saddam Hussein. One can understand why this was a story, but Trump had used similar lines about Hussein in speeches, interviews and debates several times before — for instance, in a Republican debate in February. I remember being shocked after that debate that Trump’s comments, which went so against Republican orthodoxy, hadn’t received more attention from voters and the media. I was surprised again in July, when a story that so many people had ignored in February was suddenly treated as salient.

There are a lot of cases like this. Last April, for example, the Boston Globe published a story alleging that Trump had groped a Florida woman named Jill Harth in the early 1990s. The story, despite a lot of carefully reported detail from one of America’s most prominent newspapers, was largely ignored. In October, however, after the publication of a leaked “Access Hollywood” tape on which Trump condoned unwanted sexual contact toward women, and after several more women came forward to accuse him of sexual harassment or sexual assault, Google searches for Harth’s name were about 30 times higher than they had been in April, when the Globe’s original story broke.

I had a similar haven’t-I-heard-this-one-before reaction after The New York Times published a story on Tuesday night that alleged that “members of [Trump’s] 2016 presidential campaign and other Trump associates had repeated contacts with senior Russian intelligence officials in the year before the election.” Didn’t we already know that, or at least have strong reason to suspect it? In August 2016, then-Senate Minority Leader Harry Reid wrote a letter to FBI Director James Comey asking for an investigation into ties between Russia and the Trump campaign. In October, Mother Jones and Slate published stories levelling relatively specific accusations at Trump. Then last month, BuzzFeed published a dossier, later attributed to a former British spy, that alleged that the Trump campaign had met with Russian officials, among other lurid details.

It would be one thing if Tuesday’s Times story had provided specific evidence or proof of these pre-existing claims, something those earlier stories largely lacked. But it didn’t: Their most recent story was almost entirely based on anonymous sources and was exceptionally light on specifics. In its third paragraph, furthermore, the story reported that American officials “had seen no evidence” that Russia and Trump were colluding to influence the election, only that there had been contacts between them. I’m not saying that the Times story wasn’t newsworthy, but there wasn’t really a lot there that would cause you to shift your prior views if you’d been following the news fairly carefully already.

And yet, at least as I write this on Wednesday morning, the story has blown up massively. How come? Obviously, one big reason is the timing: The story came after the resignation on Monday of national security adviser Michael Flynn, after it was revealed that Flynn had conversations with Russian ambassador Sergey Kislyak about economic sanctions on Russia, contradicting claims made by White House officials. Reporters smell blood in the water — especially with Trump acting something like a wounded animal — which made the allegations about Trump and Russia seem relevant again even if they aren’t new, exactly.

It’s noteworthy that the Flynn story — which was originally reported by the Wall Street Journal on Jan. 22 — contained a lot of specifics: detail about whom Flynn had the conversations with, when they took place, and what the subject matter was. (Subsequent reporting even revealed where Flynn was when he had the conversations — at a “beachside resort in the Dominican Republic.”) The specificity of the claims made it harder for the White House to refute them: Vague denials aren’t persuasive against specific claims, but specific denials run the risk of getting you caught in a lie. The specificity also made it easier for other news organizations, such as the Washington Post, to follow up on these stories and verify or rebut the claims.

But specificity isn’t everything: Persistence matters too. The Boston Globe’s story on Harth contained a lot of specific claims, but without news organizations following up on it or cable news shows talking about it, it couldn’t metastasize into a well-known story. Even the Flynn story didn’t blow up overnight: Based on Google search traffic, Flynn drew relatively little interest from readers until late last week, even though the Journal’s story had been published on Jan. 22. Other news organizations continuing to report out the story — and the White House bungling the response to it under increasing pressure — made a big difference in how much attention it got.

The formula behind which news stories become salient — which ones dominate the news cycle for days and weeks on end versus which ones quickly fade from memory — reflects a complex interaction between news organizations (what are their incentives?), readers (what are they watching or clicking?) and the principals behind the stories (who’s pushing the story and who’s trying to rebut it?). To some extent, it may even reflect a degree of randomness and chaos stemming from herd behavior: If a few highly influential news organizations like the Times, the Post and the Journal all decide that a story is relevant, everybody else probably will too. If they throw shade on a story, conversely, it may die fairly quickly. Ironically enough, one example of the latter result comes from the story of Trump’s ties to Russia. On Oct. 31 last year, a New York Times story (“Investigating Donald Trump, F.B.I. Sees No Clear Link to Russia”) cast doubt on the Mother Jones and Slate stories that were published that same day, and the topic of Trump’s links to Russia faded from the public conversation within a few days, only to come back with a vengeance once he was elected president.

Obviously, the inherent newsworthiness of the stories can matter too. A story about Trump groping women is more likely to blow up than one that accuses him of cheating at golf. But this can be a fairly rough correlation. On the one hand, there’s so much news that it’s hard for news organizations to cover everything at once. On the other hand, low- or medium-importance stories can feed back upon themselves and receive a disproportionate amount of attention. Your mileage may vary, but — especially in light of what’s happened since — the incredible amount of coverage devoted to Clinton’s email server during last year’s campaign doesn’t hold up very well in retrospect.

Trump can also seek to influence coverage priorities, of course. During the primary campaign, his tactic of constantly changing the subject and creating shiny objects for the media to chase often proved to be highly effective. During the general election, he wasn’t always as successful at this, instead digging in on stories such as his feud with the family of American soldier Humayun Khan, which turned minor issues into medium-sized ones. Still, Trump was often bailed out by a Clinton-related story or by reporters who lost interest and went looking for another shift in the horse race.

As president, Trump might find it more difficult to avoid sustained coverage of a single issue. The stakes for every action he takes are much greater, making him less nimble. And the media’s incentives are a lot different. I’m making generalizations, but major news organizations are usually willing to take a more openly adversarial posture toward a sitting president — especially one they don’t like — than they would be toward a presidential candidate (especially one they didn’t expect to win). Many of them would regard publishing stories that led to Trump’s resignation or impeachment as the ultimate badge of honor, in fact. If there’s any chance of that happening, the media will need fire and not just smoke — and they’ll need a whole lot of persistence when Trump tries to change the subject.