Just a headline right now at CNBC, but stand by. Business Insider heard a rumor about this before lunch but discounted it when they couldn’t substantiate it with analysts. There must be something to it, though; it’s unthinkable that CNBC would toss this grenade without something very solid to support the story. Needless to say, the fact that news is breaking within an hour after the market closed suggests that they held it back to avoid a panic and to let investors digest it over the weekend.

A downgrade, not a default, was always the real worry during the debt-ceiling saga. Moody’s and Fitch reaffirmed the U.S. as AAA (albeit with a negative outlook) a few days ago but S&P was conspicuously silent. Negotiators on the Hill believed early on that the debt package had to reduce the deficit by $4 trillion to avoid a downgrade, but S&P’s president told a congressional committee on July 27 that it wasn’t true and that some alternate plans would be acceptable.

Updates are coming. While we wait for details, read this NYT piece from last weekend speculating that the economic fallout from a downgrade would actually be modest since, after all, treasuries are still comparatively safer than any other investment. The fact that Moody’s and Fitch disagree with S&P will soften the blow too. And frankly, if there’s anything that can force the Super Committee and Congress to get serious about entitlement reform, this may be it. Or am I just putting lipstick on a very smelly pig? We’ll know soon!

Update: A government source tells Tapper they’re “expecting and preparing” for a downgrade to either AA+ or AA. Unbelievable. Here’s the spin:

Officials reasons given will be the political confusion surrounding the process of raising the debt ceiling, and lack of confidence that the political system will be able to agree to more deficit reduction. A source says Republicans saying that they refuse to accept any tax increases as part of a larger deal will be part of the reason cited.

Of course, of course. Any rather large elephants in the room missing from that litany of excuses? Here’s a hint: It rhymes with “shmentitlements.”

Update: CNBC says the downgrade could come as early as this evening. In spite of everything, I’ve never really believed that America is in decline because, well, America simply doesn’t decline. Tonight I believe it.

Update: Lots of tough talk this week from Democrats about the Super Committee, with Reid hinting that they might walk away if Republicans don’t appoint anyone willing to agree to tax hikes and Pelosi promising much harder hardball during the next round of negotiations. Let’s see what they say now.

Update: Karl from the Greenroom e-mails to remind me that S&P’s track record is a bit of a joke given that they failed to see the subprime crisis coming. True enough. Last week Zachary Karabell at the Daily Beast wondered why anyone cares what S&P thinks:

To those who say that it’s unfair to blame the messenger—and that on the whole, these agencies are simply calling it as they see it and drawing attention to real risks—there is the pesky fact that they have a legacy of either being chronically late (the mortgage crisis) or then too eager to downgrade (overreaction to the mortgage crisis). And even if they were as good as they could be, they are still simply three companies with a few hundred unelected people making calls that drive the entire global financial system.

There is one last glaring question: should these agencies even be rating a sovereign entity such as the United States? The dollar is now a global currency of commerce, and U.S. Treasuries are a form of safe-haven currency. It’s not as if the world is unaware of the economic issues of the U.S. The Chinese don’t need Moody’s to tell them about the risks of holding a trillion dollars of U.S. bonds. Shouldn’t the “creditworthiness” of the United States, or the viability of a European debt plan for Greece, be left to the determination of investors large and small worldwide along with the governments of those countries and their electorates? The success or failure of their plans will be evident soon enough, and subject to the thumbs up or down of the people, without the ratings agencies piling on or offering a view.

Mark Steyn has the counterargument to that:

Nobody in Greece, Portugal, Spain, or Ireland is talking about “out years” and exciting plans for spending cuts in 2020. They’re getting on with it now — and they’re still being downgraded.

By contrast, both U.S. political parties are playing croquet on the lawn in August 1914 — and the ratings agencies are stringing along with them. Whatever the comparisons of debt-to-GDP ratios between Greece, Ireland, and the U.S., the actual hard dollar amount involved here is of an entirely different order. The Boehner plan tells us that real fiscal discipline is impossible within the U.S. political system. At some point, the ratings guys have to call them on it — or render their system meaningless.

Right. What’s ominous about the S&P downgrade isn’t that it comes out of left field, haphazardly, but that it doesn’t. Given the long-term outlook for U.S. sovereign debt even after this week’s deal, why wouldn’t they downgrade us? Why wouldn’t anyone else? What have you seen over the past year that makes you think America’s political class is remotely equal to the task of dealing with this problem before we have a Greece on our hands?

Update: Tapper updates his post with quotes from another government official who says they’re not sure when — or even if — the downgrade will come.

Update: It goes without saying that between the downgrade and polling showing 60+% support for tax increases on the rich, the GOP will be under intense pressure during the Super Committee phase to add some new revenue to the package. That doesn’t necessarily mean tax hikes; it does necessarily mean tax reform, which might involve lower rates but many fewer loopholes. Krauthammer floats a few ideas about that today, starting with getting rid of the mortgage interest deduction.

Update: Greg Pollowitz of NRO notes that, if the downgrade happens, the U.S. will technically be a greater credit risk than Britain, Germany, and France. Given the debt contagion spreading in Europe first from Greece and now Italy and Spain, does anyone seriously believe that’s true?

Update: No idea yet if this is the truth or White House spin, but if S&P actually botched its analysis on a matter as explosive and closely watched as this, then whatever’s left of their credibility is gone for good:

A third official says that S&P made a “serious mistake” in its analysis, “based on flawed math and assumptions,” so the Obama administration is pushing back. But even though “S&P has acknowledged its numbers are wrong, it’s unclear what they’re going to do.,” the official said.

S&P refused to comment.

Update: You’ve got to be kidding: “S+P was set to downgrade. Obama admin. said their analysis off by ‘trillions’. Now S+P revising figures. Downgrade still poss.”

Update: Still waiting for S&P’s side of this, but if the White House was lying in accusing them of a trillion-dollar error, you’d expect vehement pushback. Instead, silence.

Standard & Poor’s told the U.S. government Friday afternoon that it was preparing to downgrade the U.S.’s triple-A credit rating but U.S. officials notified the S&P that they had made a mathematical error that was off by “trillions,” an administration source told CNBC.

Apparently the error was in the calculation of the U.S. debt-to-GDP ratio over time and was based on a misreading of what the correct congressional baseline was…

An S&P spokesman declined to comment on any possible plans for a downgrade or statement later Friday.

If it’s true, they’ll never recover. They’ve barely recovered from the subprime mess as it is. Then again, it could be that their math is fine and the White House is simply challenging them on a conceptual point, much like how Dems and the GOP argued this week over what tax baseline is appropriate for the Super Committee. In that case it wouldn’t be a math error, it’d be an accounting dispute.

A question from Megan McArdle, though: Who leaked this report? She wonders if the White House might have done it “just to get people yelling at the GOP,” but if that were true, why is the White House pressing so hard to get S&P change its numbers? It’s hard to yell at the GOP when the math is wrong.

Update: The Journal describes it as a “mathematical error” and claims S&P copped to it privately:

After two hours of analysis, Treasury officials discovered that S&P officials had miscalculated future deficit projections by close to $2 trillion. It immediately notified the company of the mistakes.

S&P officials later called administration officials back to say they agreed about the mistakes, though they didn’t say whether it would affect the rating. White House officials remained waiting Friday evening to see what the company would do…

A downgrade by S&P could serve as a psychological haymaker for an American economic recovery that can’t find much traction. It could lead to the prompt downgrades of numerous companies and states, driving up their costs of borrowing. Policymakers are also feeling anxious about the hidden icebergs that the move could suddenly reveal.

Imagine if this had happened during trading hours.