by Marian Wang. ProPublica, May 17, 2011, 10:08 a.m.May 16, 2011

As you may have heard, the federal government hit its $14.3 trillion debt limit yesterday—something the Treasury has been warning Congress about for months. There are a lot of good explainers out there about what this could mean. Some dig into what actions the Treasury might take; others into the oh-so-exciting history of the debt limit.

We’ve waded through them and pulled what we found to be the clearest explanations not only of what the debt ceiling is and how it works, but also the fundamentals of whether it’s necessary and why this debate may be more partisan than it is practical.

What is the debt ceiling, really?

Our friends at NPR’s Planet Money have the best explanation of this that I’ve heard. Last Friday’s podcast is worth listening to in full, but their description of the debt ceiling as a game of “Mother, May I?” is particularly helpful.

The game began in the early 1900’s, when Congress delegated to the executive branch the job of figuring out how much borrowing the federal government will need. It also gave Treasury an upper limit in order to retain some congressional control. Here’s Planet Money:

There’s something crucial to understand here. Nothing gets bought by the federal government unless Congress says so. It’s in the Constitution—the power of the purse rests with Congress. So the debt limit doesn’t actually limit the spending. It would be unconstitutional to limit the spending. It’s a safety check.

You know, I think of it as this big game of “Mother, May I?”—that old kids’ game. Congress says to the Treasury Department, “We want to buy a tank.” And Treasury looks at it and it brings us over the debt limit, and the Treasury Department has to come back to Congress and say, “Mother may I buy a tank and raise the debt limit?” And Congress votes and says, “Yes you may.” But what’s so ridiculous is that all that Treasury is asking approval to do is spend the money that Congress has told them to spend. Congress says, “Go spend this money” and acts all huffy that spending the money that Congress approved is going to get us over the debt ceiling.

So, is the debt ceiling necessary?

“Strictly speaking,” writes Slate’s Annie Lowrey, the debt ceiling is not a necessary budget tool. “By itself, it does nothing to keep the country from running into the red.”

A Congressional Research Service report notes that some budget experts have argued for getting rid of it [PDF], because the debt limit doesn’t actually change or limit spending—Congress has already authorized that spending. What it does is limit whether the federal government is allowed to pay for what it’s already spent.

The debt limit does haves defenders, who believe it has some symbolic power. According to the report, the limit “imposes a form of fiscal accountability” by forcing Congress and president “to take visible action” when the federal government spends more than it takes in:

In the words of one author, the debt limit “expresses a national devotion to the idea of thrift and to economical management of the fiscal affairs of the government.”

Where do people stand on the debt limit?

Most lawmakers—Democrat or Republican—agree that the limit needs to be raised, but they disagree on the details of what deficit-reduction measures should be attached to a debt limit deal. Reuters has a good rundown of where key leaders in each party stand.

For instance, Senate Democratic leader Harry Reid opposes making Social Security part of the discussion and favors setting targets to reduce the deficit over time. Other Democrats have called for closing tax code loopholes.

House Speaker John Boehner said last week Republicans want trillions in spending cuts in exchange for supporting a debt limit increase. But he has also said that he believes raising the debt ceiling is “necessary.” “It’s clear to me that at some point we’re going to have to raise the debt ceiling,” Boehner said in a TV appearance Sunday.

The Tea Party, on the other hand, has taken a hard line on raising the limit. “Our message has not only been no, but hell no,” Tea Party Express chairwoman Amy Kremer told ABC News. Rep. Michele Bachman, a Republican and Tea Party member, has said she’ll oppose a debt limit increase unless it includes a repeal of last year’s health care law, Reuters noted.

More than 60 trade groups—ranging from Wall Street to manufacturing—have called on Congress to raise the debt limit.

What would happen if Congress doesn’t raise the debt limit?

The Wall Street Journal’s FAQ says that government services will go mostly uninterrupted for the time being while Treasury works to conserve cash and keep paying its bills:

It has stopped issuing certain debt for state and local governments. Among other things, it can stop payments into the Civil Service Retirement system, redeem existing investment, and stop reinvestment in the exchange stabilization fund, which buys and sells foreign currencies.

The Los Angeles Times calls it a “complex fiscal juggling act” involving accounting tricks such as borrowing from federal employee pension funds.

When Treasury has done all it can and runs out of cash to pay its bills, that’s considered a default. What happens when the United States defaults is difficult to predict because it’s never happened, but the Treasury Department has warned that payments to service members, citizens, investors and businesses would be affected.

In a letter to Sen. Michael Bennet of Colorado last week, Treasury Sec. Timothy Geithner warned that defaulting would “inflict catastrophic, far-reaching damage” [PDF] to the economy—reducing growth, increasing unemployment and potentially increasing borrowing costs for the United States in the future.

So, why isn’t Congress doing it already?

One primary reason seems to be—surprise, surprise—partisanship.

“There’s always a little political theater around this,” Geithner said back in February. (That was before this debt ceiling debate had heated up, and it was even before the budget showdown/near-government-shutdown had started looking like a serious possibility.)

This New York Times graph lays out the politics of the matter pretty succinctly, and Ezra Klein explains the graph further. Basically, it depends on which party is in power in the White House and the two houses of Congress. “When Republicans are in charge, they vote to raise the debt ceiling,” Klein writes. “When Democrats are in charge, they vote to raise the debt ceiling.” Imagine that.

While we’re on the subject, it’s also worth noting that back when the Republicans controlled the White House, House and Senate in 2006, then-Sen. Obama in fact voted with his party against raising the debt limit. At the time, he called it a “sign of leadership failure” that they were even debating the matter.

That’s a quote that Obama’s political opponents are all too happy to repeat back to him now. White House spokesman Jay Carney has said the president now “thinks it was a mistake” to vote against the measure.

So, how long until Congress figures this out?

If the 2011 budget fight was any indication, there’s no telling how long Congress will take. The clock is ticking, though. The Treasury Department has said that if the debt ceiling isn’t raised, the United States will default by August 2—11 weeks from now.

Both sides have said that failure is not an option, but reports seem to indicate that they’re also not anywhere close to reaching a deal.

Follow on Twitter: @mariancw