But come March 1, it's not as if all the reductions that are planned will happen overnight.

Practically, federal workers facing furloughs must be given at least 30 days' notice. Even though a number of federal agencies said they will do furloughs, official notices aren't expected to go out until March 1 at the earliest. So actual furloughs may not occur until April.

Second, the White House budget office can tell agencies how to apportion their reduced budgets so that the effects of the funding cut might not need to occur right away. "There's some discretion," said Pete Davis, a former Capitol Hill staffer who now runs a Washington research firm.

That kind of leeway might allow lawmakers some time to figure out how to avert the full effects of the sequester.

So there's a chance the sequester could be replaced?

Yes, increasingly policy observers expect Congress will at least try to replace it by March 27, although there are no guarantees.

March 27 is the day funding for the government expires. To prevent a government shutdown on March 28, lawmakers must pass another funding bill -- if not for the rest of the year, then at least for a few weeks or months.

If lawmakers choose to replace the sequester, they would likely do so with a set of savings -- some real, some gimmicky -- elsewhere in the budget. And it's possible the savings would be realized over 10 years, rather than all in 2013.

What's wrong with the sequester?

It's a thoughtless, abrupt, poorly targeted way to cut spending. Sure, it will help reduce deficits in the near-term. But it won't do so in areas that are actually drivers of the country's debt.