Let's start with what's in the Gang of Six's plan (pdf) — or at least what we know is in it.

The first piece is $500 billion in immediate cuts and new revenue. That mainly comes through a cap on discretionary spending and slowly moving the government's measure of inflation to chained-CPI, which ends up reducing Social Security benefits and raising taxes. It also repeals the CLASS Act, which doesn't save any money in the short-term but potentially saves a fair amount in the long term, lays down some new budgetary rules and sells off some federal property.

But that's $500 billion out of a planned $3.7 trillion. So it's really what comes next that's interesting.

Entitlements come next. The proposal directs the Senate Finance Committee to find $300 billion in health savings to permanently fix the way Medicare pays doctors, and then to pull out another $200 billion in health savings — or perhaps it's $85 billion, the document is slightly confusing — on top of that. It also directs the committee to "maintain the essential health services the poor and the elderly rely on." I take that to mean structural changes such as the Ryan Plan are off the table, but things like raising the Medicare eligibility age or increasing cost sharing are fair game. Various other committees ranging from Armed Services to Energy then have to find another $250 billion or so. We're talking a lot of money here, so the cuts will have to go deep.

Then, tax reform. The code is simplified down to three brackets. Depending on how many loopholes and breaks the negotiators want to eliminate, the brackets will be between 8 and 12 percent for the lowest bracket, 14 and 22 percent for the middle bracket, and 23 and 29 percent for the top bracket. Notably, the Finance Committee is directed to leave the Earned Income Tax Credit and the Child tax Credit, both of which are hugely important to low-income folks, untouched.

But though some of that money is going to lower brackets, the reforms must raise more than $1 trillion in new revenue — including $133 billion for infrastructure. The plan also appears to build the expiration of the Bush tax cuts for income over $250,000 into the baseline. So the total amount of revenue raised might be closer to $2 trillion, if you're counting against where we are now. Of course, if you count against the expiration of the Bush tax cuts, it's a tax cut of about $1.5 trillion. Finally, the plan also calls for revenue-neutral corporate tax reform.

Then the Budget Committee is charged with drawing up legislation to extend the caps on discretionary spending — which cover both defense and non-defense, and, if I understand this right, cut more than $1 trillion from projected spending — until 2021, and to draw up an enforcement mechanism that will kick in if deficit reduction isn't on track come 2015. Come 2020, federal health spending is put on a global budget, with growth not to exceed GDP plus 1 percent.

Finally, once all that's passed, the Finance Committee is asked to produce legislation making Social Security solvent for the next 75 years, and their product is assured certain procedural advantages. There's very little in the way of specifics here, but there's an odd line suggesting that if this effort fails, then the vote on the whole deficit-reduction plan is invalidated. That sounds wrong to me, so I'll check into it. 

All in all, it looks a lot like the Simpson-Bowles plan, which was pretty much the point of the exercise. A few weeks ago, I wrote a column arguing that, in retrospect, the Simpson-Bowles plan was a pretty good deal: It was more balanced on both the spending and the tax side than the president's April deficit-reduction proposal. I think that it is, if anything, truer now than it was then, and truer in this bill than it was in that bill. This bill, for instance, appears to jettison the Simpson-Bowles recommendation that tax revenues be capped at 21 percent of GDP.

It's become quite clear that a big deficit bill will be more balanced than a series of small bills. It would also be nice to get deficits off of the agenda for awhile so the political system could do other things. And though this doesn't get much attention, you can get more actual reform in a big bill — think of the difference between overhauling the tax code and simply raising rates slightly, or the difference between changing how Medicare pays doctors and simply cutting benefits — than you can out of a small bill, which ultimately means you're making better policy. So though there's lots to argue with in this bill, and lots that I, personally, would like to change, I don't think there's much doubt that it's far better than what Congress is likely to do — or not do — if it fails.

What's also interesting is that we're effectively seeing something of a do-over. Simpson-Bowles didn't really get the support of any of the senators on the committee. They all said they wanted to make changes. Now, they have. Many politicians — a number of them on the right — blasted President Obama for dismissing the Simpson-Bowles plan rather than making it his own. In remarks this afternoon, he said the Gang of Six's product is "consistent" with his principles and made it pretty clear that if the House and Senate agree on a variant of this plan, he'll sign it. So what we have here is a bipartisan deficit-reduction plan that hits the $4 trillion target — or at least gets very close — and carries presidential support. Now we find out if such a thing can actually pass.