This story was breaking as the president was preparing to give his jobs speech last night, which some critics who possess a lively imagination believe there might be a connection. Brent Baier of Fox News said as much after the speech - that the White House was manipulating the news for maximum effect.

I don't find that credible for the simple reason that the last thing the White House wanted was a distraction from Obama's jobs speech. It was clear from the way he delivered the speech that the president believes his proposals will help create enough jobs to kick start employment. The fact that the chances of that happening are slim and none is beside the point. Like everything else they have tried - and failed at - these guys, clueless though they might be, actually think their ideas will help.

That said, how much more serious is this threat than any of the dozens of others that have appeared on our threat radar over the last 10 years? ABC News:

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.

Officials say the alleged terror plot was initiated by new al Qaeda chief Ayman al-Zawahiri, Osama bin Laden's successor, who had pledged to avenge bin Laden's death earlier this year in a U.S. raid.

Intelligence and law enforcement officials told ABC News that at least one of the individuals is a U.S. citizen and one official said that two of the individuals may have had U.S. documentation -- whether green cards or passports was unclear.

The threat was described as specific and credible by federal officials. "Al Qaeda has shown an interest in important dates and anniversaries. In this instance it is accurate that there is credible, specific but unconfirmed information," said Janice Fedarcyk, FBI Assistant Special Agent in Charge of the New York office, at a Thursday evening press conference.

At a the same press conference, New York City Mayor Mike Bloomberg said the NYPD was already on alert because the anniversary is seen by terrorists as an opportune time to strike, and would be deploying additional resources around the city. He also said that the threat was credible and had to be taken seriously, though "it has not been corroborated."

The general info on the threat was developed from intel we got in Abbottabad after killing Osama. Allah takes that one step further and points to the recent capture of al-Qaeda's international operations chief in Pakistan as a possible source for more specific information:

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.

That latter suggestion by Allah cannot be discounted. AQ has had 10 years to strike us again and have been unable to mount the kind of mass casualty operation that they so dearly love to carry out. It may be that we remain one step ahead of them and nip these plots in the bud before they can be brought to fruition. I suspect most of the plots we foil will be a long time seeing the light of day for the simple reason that reporting on them would reveal sources and methods best kept secret from the enemy.

But using western looking Americans is a new wrinkle and it sounds credible to the untrained ear. Washington and New York seem to be likely targets but this Sunday is the opening of the NFL season for most cities, and other targets cannot be discounted. There are also some significant college football games on Saturday, and the usual run of targets including subways, landmarks, and shopping malls.

Vigilance will only take us so far. Up to now, 10 years after 9/11, I think it correct to say that in addition to all our sophisticated anti-terrorism tools, simple, dumb luck has also played a role in our avoiding another attack.

Let's hope our luck continues to hold.