An open letter to Treasury Secretary Tim Geithner on how to avoid the fiscal cliff: Stop acting like a policy wonk and start acting like a Wall Street dealmaker.

Treasury Secretary Tim Geithner

FORTUNE -- Dear Mr. Secretary:

I know that even though President Obama has been reelected, you are planning to leave the Treasury. So I'd like to offer you a goodbye gift. It's not money or a prestigious seven-digit-a-year gig. It's a way to avoid having the government blackmailed because our national debt ($16.206 trillion the last time I checked) is approaching the national debt ceiling ($16.394 trillion) and will breach it in December.

You remember the debt-ceiling debacle in August 2011, when the Treasury came within a whisker of defaulting on its obligations because of the antigovernment, innumerate fanatics in the House of Representatives. For all the post-election talk of cooperating to solve the "fiscal cliff" problem -- much of which stems from last year's debt-ceiling gamesmanship -- the same fanatics are still in power in the House. These are the people who so enraged me that I left the Republican Party, as I said I would in the rant I wrote for Fortune's Sept. 5, 2011, cover story, titled "American Idiots."

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Look, I hate the fiscal path that our country is on. I hated it under George W. Bush, and I hate it under Barack Obama. The solution is obvious, along the lines that my colleague Geoff Colvin and I proposed in September 2012: broadening the tax base so that we can lower rates while increasing tax revenue; treating income from capital and work the same way; and trimming the growth of entitlement programs such as Social Security and Medicare, especially for people like me who are well off. Much of this has become the conventional wisdom in Washington -- and it's actually wise.

But having a crisis about the federal government's ability to pay its bills is unwise. It won't resolve our fiscal problems. All it will do is make people on both sides of the divide even more frustrated and angry than they already are.

So here's my unsolicited and probably unwelcome advice. Rather than risk breaching the debt ceiling in December and having the government run out of cash in January, think like a smart Wall Street deal guy instead of a cabinet secretary. (Yes, Wall Street has a bad rep these days, most of it deserved. But so what? If Wall Street has something useful to offer, use it.)

Okay, now here's what I propose: Make a private deal with a central bank of a country that has huge holdings of Treasury securities (for instance, China) and doesn't dare risk having a default on the interest or principal due on its holdings. Let's borrow $200 billion by doing this, giving our lender a 10-year security that the Treasury can redeem early if it chooses to. While Congress is playing its destructive game of chicken, you can keep the government functioning and be the hero who helped us avoid an economic calamity. The Treasury will have to pay an above-market interest rate on this borrowing. But you can score points -- well-deserved ones -- by blaming House obstructionists for the added taxpayer expense.

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Would lawyers bless this maneuver? Who knows? But if you don't ask them, they can't say no. You'll be playing offense instead of defense with John Boehner and his crew. Even if they run shrieking to the Supreme Court to reverse the deal, do you think the Supremes' majority, who made the political decision to uphold the major elements of Obamacare (a.k.a. the Affordable Care Act), would force the Treasury into a debt default? I doubt it. You or your successor can repeat this private-placement maneuver as often as necessary to keep the government's ability to pay its bills intact.

I hope that a compromise is reached quickly and that my suggestion proves to be moot. But be prepared. And remember, don't talk about this proposed transaction during debt-ceiling negotiations. Line it up secretly and -- as Nike would say -- just do it. Normally, I'd ask for a huge fee if the Treasury uses my somewhat outré idea. But as my contribution to the public fisc, I'll settle for a shout-out. Call this the Sloan Stratagem, and I promise not to bill you.

And on that note, all the best on your new gig, whatever it proves to be.

This story is from the December 3, 2012 issue of Fortune.