In some corners of the universe, it was a bombshell. President Trump would be bringing none other than Tony Bobulinski to the second and final presidential debate on Thursday night, a decision sure to shake the foundation of the presidential race.

In most corners of the universe, though, the response was a bit different: Tony Who-now?

There are two patterns that have so far defined Trump’s effort to win a second term. The first is that his campaign seizes upon particular themes and shakes them ferociously like a dog that’s nabbed a squirrel. The second is that these themes often overlap with the obsessions of conservative media, both because they often emerge from that world and because they often inform it.

So we’ve seen these waves. Former vice president Joe Biden is addled! — which lasted until the Democratic convention, and it was pretty obvious that Biden was perfectly capable of offering an extensive rejection of Trump’s first term in office. Leftist thugs are burning down cities! — an argument that evaporated along with the summer’s rash of protests and, one assumes, polling showing that it wasn’t doing any good.

The most recent obsession in Trump’s universe is Biden’s son Hunter. Hunter Biden’s rocky background is no secret, with Joe Biden himself having addressed it on several occasions. Last week, though, the New York Post began running a series of articles leveraging material obtained by Trump’s attorney, Rudolph W. Giuliani. The initial focus was on re-litigating the events that led to Trump’s impeachment last year, though much of the attention was instead focused on the odd provenance of the material. In reporting from the New York Post and Fox News since, the focus has expanded outward to include other aspects of Hunter Biden’s business record.

That’s where Mr. Bobulinski enters. A former business partner of Hunter Biden’s, he apparently became frustrated at learning that the former vice president’s son had made a business deal in China without him. He’s since decided to help Giuliani and Senate Republicans dig through as much of Hunter Biden’s business history as possible. His presence at the debate, it appears, is either meant to rattle Joe Biden for unclear reasons — or simply to inject more energy into Trump’s base, many of whom have been tracking the expanding intricacies of the Hunter Biden plotline with great enthusiasm.

It is, for example, a staple of Fox News’s coverage, with Hunter Biden’s name arising repeatedly on both the main network and its sister, Fox Business. It’s barely been mentioned on CNN or MSNBC.

As with Trump’s fixation on crime and violent protests (the vast majority of which were, in fact, not violent), this obsessive consideration of the actions of Hunter has not had any significant effect on Joe. The first New York Post story came out on Oct. 14. Since then, Biden’s national lead in FiveThirtyEight’s average of polls has fallen a statistically insignificant 0.3 points. In some swing states, the lead has narrowed a bit more, but not demonstrably because voters there are particularly worried about what Biden’s son was doing.

We’ve included the late trend from 2016 polling because it’s essential that Trump begin eating into Biden’s leads in most of these states if he is to have a chance at a second term. Each day that goes by with Trump throwing more energy into the Hunter Biden plotline (or feuds with CBS News journalists) is a day on which more voters cast ballots and on which the opportunity for Trump to close that gap escapes.

After all, it’s not just that the polls narrowed nationally and in, say, Pennsylvania. It’s that they narrowed from a much wider deficit than in 2016. Earlier this week, we looked at how the current race (solid lines) compares with 2016 (dotted lines) on three metrics: overall support, the margin between the two candidates and the pool of undecided voters. The graph below (which updates automatically) shows the comparison. There are fewer undecided voters who might shift to Trump this year, and Biden’s over 50 percent in many places.

Yes, the national gap narrowed — but Biden’s still up by about 10 points.

Your browser cannot display this graph.

(These data come from FiveThirtyEight’s averages.)

Trump’s defenders will argue that voters don’t know Bobulinski’s name because most news outlets haven’t dived deep enough into the story to cover that level of nuance. Which is largely true, in part because most news outlets (including, at first, Fox News) were unwilling to cover the initial allegations reported by the New York Post given the inability to access and verify the material.

We’ve seen similar patterns play out repeatedly over the past four years. Conservative media seizes upon an allegation and plays it out to the millionth degree, isolating specific capillaries as smoking guns. Eventually, more reporting reveals that the allegations were overblown, misrepresented or false, and everyone moves on the next thing.

A great, albeit accidental, example came from the Trump campaign’s own rapid response team on Wednesday night. It wanted to slam the press for not covering the Hunter Biden story, so it dug into its archives for a GIF of Leslie Nielsen in “The Naked Gun” trying to disperse a crowd watching a fireworks factory explode.

The only problem was that, instead of simply embedding the GIF, they embedded the entire tweet from which it came. This tweet:

The “unmasking scandal” was a staple of both Trump and his allies for years. The details don’t matter much here, but the upshot is simple: A probe commissioned by Attorney General William P. Barr determined there wasn’t any scandal at all.

In other words, the Trump campaign was criticizing the media for not covering something the way it wanted — but the example it used was one in which the way it wanted the incident covered was wrong.

The account quickly realized its mistake and tweeted this:

This is what they hope will define the last 12 days of this race. This is why Bobulinski is going to the debate.

Whether the result is any different from “unmasking,” either in disparaging Biden or moving the polls, remains to be seen.