They’ve got to try something. In the span of four months, they’ve lost Bin Laden, their operational chief (and new number two) Atiyah al-Rahman, and most recently a senior operative known as Younis al-Mauritani who was tasked by Osama himself with plotting international attacks. We’re picking their bones clean. If they can’t get someone somewhere inside the U.S. to do something this weekend to mark their most momentous plot, it’ll be proof positive of how far they’ve fallen in a decade.

Whatever it is, it’s serious enough that Obama’s been briefed on it more than once.

The threat would target New York City or Washington, D.C., sources said. Authorities have obtained what they believe is information on possible suspects tied to central Al Qaeda, but they have not necessarily determined names of possible suspects…

According to a senior U.S. official with knowledge of the threat, “People are aggressively pursuing leads,” and it is “specific enough to elicit worry.” Another senior U.S. official stressed the threat is still “unconfirmed” so it is being chased down and investigated…

“It feels more than aspirational,” one official said.

A U.S. official told the local NBC affiliate that the plot may involve car bombs and “threats to bridges and tunnels’; a reporter at CBS hears that the feds are trying to locate five to 10 people connected to it. A different official tells NBC that the intelligence came in “very, very recently” and that he’d rate the seriousness of the threat as a five or six on a scale of one to 10 — although he qualified it by saying it’s neither imminent or confirmed. (How is an anniversary attack not “imminent”?) I’m mighty curious to know how they were tipped off. Do note: Although al-Rahman and of course Bin Laden were killed, al-Mauritani was actually captured in a joint CIA/ISI operation somewhere near Quetta in Pakistan. No one’s saying when, precisely, they grabbed him, but this nifty short bio in Spiegel suggests it might have been a week or so ago. All of that fits the basic outline of what we know here: al-Mauritani was the guy in the inner circle who was focused on attacking America, his arrest was probably very recent, and he is indeed a member of “central Al Qaeda,” not one of the offshoots in other countries. Maybe he coughed something up during interrogations? Or maybe there’s no plot and he’s merely waging a little psychological warfare from his cell to try to convince us that something’s in the works.

Daniel Henninger has a piece out today at the Journal noting that while much has changed since 9/11, America’s counterterror arsenal has remained remarkably consistent from Bush to Obama. Can’t wait to find out which Bushian tactics may have been used to dig up this hot lead.

Update: Be careful out there.

More FOX reporting — a law enforcement source says terrorists were saying, “We need to get our people into place” for a car bomb

Update: ABC says they’re looking at three people at least, one of whom may be an American citizen.

U.S. authorities are scrambling to sort through information that the CIA developed in the past 24 hours indicating that at least three individuals entered the U.S. in August by air with the intent to launch a vehicle-borne attack against Washington, D.C. or New York around the anniversary of 9/11, according to intelligence officials.

One of the intelligence and law enforcement officials that ABC News spoke to said that one of the individuals may be a U.S. citizen and a second official said that possibly two of the individuals may have had U.S. documentation — whether green cards or passports was unclear…

Although authorities said they had not yet identified the suspects, the operatives are believed to have embarked on their journey to the U.S. from the tribal areas of Pakistan, according to two senior officials. One official said the route may have taken them through Dubai.