Since 1947, the Bulletin of the Atomic Scientists at the University of Chicago has maintained "The Doomsday Clock." The more the hands inch toward midnight, the closer the world is creeping toward nuclear destruction.

The scientists have maneuvered the clock's hands 19 times. Each repositioning of the hands corresponds to global events, reflecting how near or far the world is to impending doom.

The scientists slid the hands back to 17 minutes to midnight following the 1991 incineration of the Soviet Union. That marked the furthest the hands have ever been from midnight. They were closest to midnight in 1952. The scientists set the clock at two minutes to midnight after both the U.S. and U.S.S.R. pursued the hydrogen bomb.

"Only a few more swings of the pendulum, and from Moscow to Chicago, atomic explosions will strike midnight for Western civilization," wrote the Bulletin of the Atomic Scientists.

If there were a similar timepiece to monitor how close the government was to shutting down Saturday morning, it's likely the hands of that chronometer could be set at two minutes to midnight. Government funding ceases at the end of the day Friday. And just after 9 pm last night, President Obama convened a conclave with House Speaker John Boehner (R-OH) and Senate Majority Leader Harry Reid (D-NV).

Even if there isn't a Doomsday Clock to trace how close the government is to operational Armageddon, another clock is working against negotiators. A "deal" doesn't mean that it can breeze immediately through both chambers of Congress and head to President Obama's desk.

Here's why: House Republican leaders insist on enforcing the "three day" rule. The GOP says this is in response to Democrats "rushing" bills through the House without granting lawmakers enough time to read and contemplate legislation. So the GOPrequires the House to post legislation for three days before lawmakers can debate an issue. There's much confusion about how to interpret this maxim. But Rule XIII of the House indicates that it's not in order to consider a bill until its been available on three calendar days. Sources familiar with this proviso tell FOX that a loose interpretation of this rule means the House could post a bill just before midnight on say a Monday, allow Tuesday to pass and then debate the package just after midnight on Wednesday.

Regardless, that could chew up a lot of time with the Friday night deadline pressing. And don't forget that Republicans made significant political hay off chastising Democrats for not giving them enough time to "read the bills" in the last Congress. Republicans could face a backlash from the tea party if they fail to adhere to the three day rule.

Then there's a second problem: House Appropriations Committee Chairman Hal Rogers (R-KY) says if the sides do forge an agreement, it requires considerable work to prepare legislation of this magnitude for the floor.

"This will be a huge bill," Rogers said. "We need drafting time. It takes a few days."

And even if the package slides through the House, there's the United States Senate. Any senator could conceivably filibuster. That requires Reid to file a "cloture petition" to shut off debate. By its nature, a cloture petition must "ripen" for two days before the Senate can even vote to end debate. And a cloture vote needs 60 yes votes to pass.

So, time is on no one's side right now. That means chances for a government shutdown are very real. Even if the sides carve an agreement.

That could be the grand irony here. The president, Boehner and Reid broker a bill, but the government shuts down anyway while they dot the i's and cross the t's.

There's precedent for this.

Everyone on Capitol Hill is chattering about the legendary series of shutdowns in late 1995 and early 1996. But perhaps a better model to examine is an often-forgotten shutdown in October, 1990. A rebellion by House Republicans helped torpedo a major deficit reduction plan backed by President George H.W. Bush. In an effort to jar Congress's attention, the president vetoed a stopgap spending measure to run the government and delved back into negotiations on the deficit reduction package.

Bush's veto triggered a three-day government shutdown over Columbus Day weekend while the sides hammered out a new agreement. The shutdown was hardly a crisis, as the government shuttered the national parks and Smithsonian Museums. But then-Senate Majority Leader George Mitchell (D-ME) crowed that the president's "decision to shut down the government is wrong and unnecessary."

In other words, a limited shutdown could have little operational impact. But after weeks of white-hot rhetoric, a shutdown of any sort in today's supercharged atmosphere would carry major political consequences.

For instance, freshman Rep. Billy Long (R-MO) called President Obama "President Cellophane," for what the Congressman perceived as the president's absence on the issue. It's a take on the song "Mr. Cellophane" from the musical "Chicago."

"Mr. Cellophane needs to come to the table and quit telling us to act like adults," admonished Long.

Rep. Kevin Brady (R-TX) suggested that the president was out of touch on the issue for so long that lawmakers "thought about sending out an Amber Alert."

Everyone knew where Mr. Obama was late Wednesday night as he huddled with Boehner and Reid for 90 minutes at the White House. The president briefly addressed reporters in the briefing room and then the two Congressional leaders made an extraordinary, joint appearance in the White House driveway.

"We've narrowed the issues significantly," Reid said.

"I do think we made some progress," said Boehner, who did add a cautionary note. "There is no agreement on a number. No agreement on policy riders."

But the mere fact the Boehner and Reid appeared in tandem and said anything at all signaled the talks were moving in the right direction.

But House Republicans think they have a way to keep the government open on Thursday.

When the House approved the latest temporary spending bill to fund the government a few weeks ago, 54 House GOPers bucked leadership and voted no. In fact, Republicans could only lose 27 of their own members without needing votes from Democrats to keep the government operating. Many of those Republican defectors said they were weary of stopgap bills, wanted deeper cuts or specifically asked for policy add-ons, known as "riders." These "riders" would defund the health care law, strip Planned Parenthood of federal dollars or restrict the EPA from regulating CO2 emissions.

Any legislation like that can't secure the necessary votes in the Senate and President Obama is loathe to sign it. And a growing number of GOP lawmakers swore off voting for any more temporary bills.

So earlier this week, the House Republican brass cooked up another interim measure. This "Continuing Resolution" (known in Congress-ese as a CR) would run the government for a week, slash $12 billion and pay for Pentagon programs for the rest of the fiscal year.

This is quite a gambit for John Boehner. There was growing concern among conservatives that Boehner might "cave" to a deal. But Boehner's bill helped eliminate skepticism on the right. First, the cuts are significant. Secondly, the bill sends the military the money it needs. That alone challenges both Democrats and Republicans to vote for the armed forces.

Last week, freshman Rep. Lou Barletta (R-PA) was quick to say he wouldn't vote for any additional CR's. But by Wednesday night, Barletta changed his tune.

"This is not a typical CR," said Barletta, who described the military sweetener as "icing on the cake for me."

House Majority Whip Kevin McCarthy (R-CA), the GOP's top vote counter, bragged that unlike the last temporary bill, he wouldn't need Democratic assistance.

"We don't need one Democratic vote," predicted McCarthy. "If Democrats don't want to join us, that's fine."

But in many respects, this bill was a dare to the Senate. In short, the House GOP was challenging Senate Democrats to defy them by voting against funding the troops or face a government shutdown over the weekend. Reid was quick to declare the legislation a "fantasy" and a top Senate leadership aide doubted the House GOP's CR would see the light of day.

Rep. Alcee Hastings (D-FL) excoriated his GOP colleagues for trying to box in his colleagues across the Capitol.

"You know this ain't going nowhere in the Senate," groused Hastings.

That's why at a meeting of the House Rules Committee, Rep. Norm Dicks (D-WA), the leading Democrat on the Appropriations panel, implored lawmakers to approve a "clean" CR until the sides could bridge the impasse. In Capitol Hill talk, a "clean" CR means it has no extra policy riders or additional spending cuts. It just keeps the government open for a few days at the existing funding levels. And that's precisely the type of bill that many Republicans warned Boehner that they wouldn't support.

So even if there is a deal, the government's doomsday clock stands at two minutes to midnight.

"It may require a plain, old CR," conceded Rogers, a reference to Dicks's plan to keep the government operating.

Many Republicans would prefer a CR with cuts and policy sweeteners. But on Wednesday, Boehner proved his commitment to conservatives by forging ahead with the deeper spending cut bill that runs the military. In addition, that legislation contains two policy riders that appeal to Republicans. The package would essentially require that terror suspects be tried at Guantanamo Bay. The legislation also bans the use of federal and local dollars for abortions in Washington, DC.

However, a vote on that bill Thursday could give Boehner the political cover necessary to trot out a "plain, old CR" to avert a shutdown and buy Rogers time to author the final bill.

And if that happens, only then can someone move back the hands on the "Doomsday" government shutdown clock.