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The game is the same, but many of the players have changed. Congress and the president are facing off in another supreme spending showdown. If they don't agree on a funding bill by the end of September 30, much of government will shutdown. This last happened in 2011, when Congress avoided a shutdown by passing a spending measure shortly after the midnight deadline hit. Who controls what happens this time? Take a look at the key players who will determine how this fight ends: -- From CNN Capitol Hill Reporter Lisa Desjardins. CNN's Deirdre Walsh and Ted Barrett contributed to this report.

Rep. Mark Meadows, R-North Carolina -- The architect. During Congress' August recess, the tea party-backed freshman wrote to Republican leaders suggesting that they tie dismantling Obamacare to the funding bill. Though initially rejected by GOP leadership, 79 of Meadows' House colleagues signed on to the letter, which quoted James Madison writing in the Federalist Papers, "the power over the purse may, in fact, be regarded as the most complete and effectual weapon ... for obtaining a redress of every grievance."

Speaker John Boehner, R-Ohio -- The coach. He'll make the key play call. The top Republican leader in the land may be the most important player in the days immediately before a possible shutdown. Boehner could decide whether to push through the Senate's version of a spending bill and keep government running, or he could float a third version with some other Republican wish list items in it. If he takes the second option, Boehner could risk a shutdown but could also force the Senate into a tough position: give House Republicans something or send federal workers home. Timing on all this will be critical.

Sen. Ted Cruz, R-Texas -- The revolutionary or rabble rouser, depending on your viewpoint. The tea party firebrand could lead a long filibuster on the Senate floor, delaying passage of a spending bill until just one day before the deadline on Monday, September 30. Cruz has stoked the anti-Obamacare flames all summer, but recently angered fellow Republicans by openly saying that the Senate does not have the votes to repeal the health care law.

Sen. Marco Rubio, R-Florida -- Senator to watch. The potential presidential candidate has been one of three senators (Cruz and Mike Lee, R-Utah, being the others) pushing to use the government shutdown debate as a way to repeal or defund Obamacare. But watch his actions and language as a shutdown nears to see if he digs in or if downshifts at all.

Sen. Harry Reid, D-Nevada -- The man steering the ship in the Senate. Master at using Senate procedure to his advantage, Reid is the main force in controlling the voting process in the chamber and ensuring that an attempted filibuster by tea party-types fails. The majority leader will be a primary negotiator if we reach phase three, if the House does not accept the Senate spending bill.

Sen. Mitch McConnell, R-Kentucky -- If Reid steers the ship, McConnell controls the headwinds. Which is good news for Reid, at least initially. The Republican leader and several of his members say they will vote against Cruz's filibuster and in favor of a spending bill with no limits on Obamacare. Meaning, in favor of a bill that just funds government. McConnell generally has been leery of running into a shutdown or default. In fact, one legislative method for avoiding default is named after him.

Sen. Patty Murray, D-Washington -- The consigliore. Murray, center, does not seek the outside limelight, but the Senate Budget Committee chairwoman is a major fiscal force behind the scenes on Capitol Hill. Known by fellow Democrats as a straight shooter, she is also an experienced negotiator, having co-chaired the laborious, somewhat torturous and unsuccessful Super Committee.

Rep. Tom Graves, R-Georgia -- The new militia leader. The freshman congressman from Georgia, second from right, is one reason the debate has reached this point. Graves led the charge that blocked the original proposal by House Republican leaders. That would have kept government funded and had a detachable portion on Obamacare. Instead Graves and other conservatives forced their leaders to pass a spending bill with a mandatory defunding of Obamacare.

Rep. Peter King, R-New York -- The blunt statesman. King is outspoken against many tea party tactics, calling the move to tie Obamacare to the must-pass spending bill essentially a suicide mission and Cruz "a fraud." He is pushing for Republicans to accept a more "clean" spending bill that can pass the Senate and avoid a shutdown.

Thomas Donohue, president and CEO of the U.S. Chamber of Commerce -- The heavy. Donohue is known for his deep connections and his aggressive lobbying on behalf of business. He and the Chamber are urging Republican lawmakers to avoid a shutdown. The Chamber is an important political backer for conservatives, but has had mixed success with the current Congress, locking in firm anti-tax positions but unable to push through immigration reform so far.

Michael Needham, president of Heritage Action -- The driving force. Needham runs the political offshoot of the conservative Heritage Foundation and has been unrelenting in urging lawmakers to repeal Obamacare. He has told Republicans not to fear a potential shutdown, saying they would suffer more politically from allowing Obamacare to continue.

President Barack Obama -- The campaigner and CEO. Expect the president to use his podium more as a shutdown nears, aiming at public opinion as Democrats in Congress position themselves. If House Republicans send back a new proposal close to the September 30 deadline, the president and Democrats will have to decide what move to make next.

Rep. Eric Cantor, R-Virginia -- The powerful lieutenant. Cantor, the House Republican No. 2, is much more closely allied with conservatives and tea party members in the House than is Speaker Boehner. The two have not always agreed on every strategy during potential shutdown debates, but have been in public lockstep during the current go-around.

Rep. Nancy Pelosi, D-California, and Steny Hoyer, D-Maryland -- Players on deck. The top two House Democrats are mostly watching and waiting. But they will play a critical role once Boehner decides his next move. They could either bring Democratic votes on board a deal or be the loudest voices against a new Republican alternative. Hoyer will be interesting to watch; he has strongly opposed both the House and Senate plans as cutting too much in spending.

Rep. Kevin McCarthy, R-California -- The numbers guy. McCarthy, the House whip, has the tricky job of assessing exactly where Republican members stand and getting the 217 votes it takes to pass a bill in the chamber. He is known for his outreach to and connection with many of the freshmen House members who align with the tea party.

Rep. Paul Ryan, R-Wisconsin -- Member to watch. The vote of the House budget chairman and former vice presidential nominee is an important signal both within Republican ranks and to the public at large. Ryan has voted against some funding measures in the past, including the emergency aid for Superstorm Sandy recovery. But he was a "yes" on the last extension of the debt ceiling.

Rep. Ileana Ros-Lehtinen, R-Florida -- Another member to watch. A former committee chairwoman (Republican rules have term limits for committee chairs), Ros-Lehtinen knows House politics and procedure inside out. Depending on the issue, she has been described as a conservative or moderate, and occasionally as a libertarian.

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(CNN) -- Let's start with the obvious question: Will the government shut down this week? Most likely.

Republicans and Democrats can agree on that. It's everything else that has them bickering and blaming. And unless they strike a deal on a spending bill Monday, the government will begin closing shop at 12:01 a.m. Tuesday.

After weeks of congressional back-and-forth, the ball is now in the Senate's court. It meets at 2 p.m. Monday to decide what to do next.

A shutdown, while likely, isn't a foregone conclusion. The deadline is midnight -- and one day can be a long time on Capitol Hill.

Political effect of a governent shutdown

Media coverage of Obamacare, shutdown

Obamacare: 'Duct tape and chicken wire'

GOP Rep: Senate is 'playing games'

Here's a quick Q&A to get you caught up on what happened over the weekend and what to look forward to Monday.

1. Why would the government shut down?

Congress has one key duty laid out in the Constitution -- pass spending bills that fund the government. If it doesn't, most of the functions of the government -- from paying the military to funding small business loans to processing passport requests -- would grind to a slow-motion halt.

2. Why does it have to pass a spending bill in the middle of the year?

It may be the middle of the calendar year. But the government's fiscal year runs from October 1 to September 30.

3. What's the holdup?

House Republicans insist the spending bill include anti-Obamacare amendments. Senate Democrats are just as insistent that it doesn't.

4. How is Obamacare tied to funding the government?

The health care law isn't directly tied to funding the government, but it's being used as a bargaining chip. A group of Republicans, led by freshman Sen. Ted Cruz of Texas, despises the president's signature health care plan so much that it's willing to risk government shutdown or default.

5. What are some of the objections to Obamacare?

The Patient Protection and Affordable Care Act, the actual name of the law, requires all Americans to have health insurance. Opponents say it'll hurt employers and amounts to overreach by the federal government. Some have also criticized the medical device tax that's part of the law, saying that by imposing such a tax, it's basically sending jobs overseas.

6. What's the Democrats' defense?

They say the law will expand access to health care and help rein in the rising costs of coverage. Obamacare prevents those with pre-existing medical conditions from being denied health insurance, and proponents say those who have health insurance will no longer have to indirectly pay for those who show up in emergency rooms uninsured.

Fact check: The myths and realities of Obamacare

7. What happened with the spending bill over the weekend?

The Republican-dominated House passed two spending bill amendments Sunday morning -- one that would delay Obamacare for a year, and one that would repeal the Obamacare's medical device tax. The bill now goes back to the Senate, where Democrats who control that chamber have consistently said any changes to Obamacare would be a deal-killer.

8. What happens Monday?

The Senate will meet at 2 p.m. ET -- 10 hours before the deadline. It'll "do exactly what we said we would do and reject these measures," Senate Democratic Leader Harry Reid said. "The American people will not be extorted by Tea Party anarchists."

In other words, the Senate will send its version of the bill -- one without any changes to Obamacare -- back to the House.

Rep. Tim Griffin of Arkansas said the Senate is running out the clock. "At some late hour, they'll pass something and then they'll say 'Oh my gosh, we've run out of time.'"

9. So is there any hope?

You could look at the glass-half-full scenarios.

-- Sen. Rand Paul told CBS' "Face the Nation" the two chambers of Congress should go to conference. Such committees are common when both houses pass competing bills and need to reconcile the differences. Senate Democratic Whip Dick Durbin Durbin said he's open to talking with Republicans, "but not with a gun to my head."

-- If the Senate rejects the bill, the House will reconvene "in enough time" and send another provision, House Majority Whip Kevin McCarthy told "Fox News Sunday." But he said the next bill the House passes will involve Obamacare in some way.

10. If nothing changes, does the government shut down?

Yes, for the first time since late 1995. That one lasted 21 days, into 1996.

11. How will it happen?

There won't be a thunderclap or clang of bells. First order of business? Draw up a dividing line between workers deemed essential or non-essential. Those in the first category will carry on operations. The others will power down until Congress comes to its senses and funds the government.

So, for example, park rangers would start locking up national parks. And most furloughed federal workers are supposed to be out of their offices within four hours of the start of business Tuesday.

12. How many government workers could be furloughed?

Most of the 3.3 million government workers are deemed "essential" -- they'll keep working. But more than 783,000 government employees will sit at home, according to a CNN analysis of contingency plans published by the federal government on Friday. Not all government agencies submitted contingency plans.

13. What will this do to the economy?

Depends on how long it lasts. If it's just a few days, the hit might not be severe. But three or four weeks? "(That) would do significant economic damage" -- reducing GDP by 1.4 percentage points for the quarter, says Mark Zandi, chief economist and co-founder of Moody's Analytics.

14. How will this affect me?

In ways big and small. The mail will continue to come. The military will continue to fight. And Social Security checks will continue to be paid.

But if you need a federal loan to buy a house, you'll have to wait. If you want a gun permit or a passport, that won't happen anytime soon.

15. Will a shutdown kill Obamacare?

Probably not. Most of the money for Obamacare comes from new taxes and fees, as well as from cost cuts to other programs like Medicare and other types of funding that would continue even if the government shuts down.

16. Will the president get paid during a shutdown?

Yes. His salary -- $400,000 -- is considered mandatory spending. It won't be affected.

17. What about House and Senate members?

They'll keep drawing checks, too.

18. What does John Q. Public think of all this?

A CNN/ORC International poll that came out Monday found that 46% will blame congressional Republicans if the government closes its doors, with 36% saying the president would be more responsible and 13% pointing fingers at both.

19. Is there any hope if a deal isn't struck by midnight?

If lawmakers reach an agreement by late Monday night, but the funding bill hasn't made it to the president's desk, the government can ignore a short lapse in funding and carry on in good faith knowing that it will. The last time that happened was in April 2011.

20. Isn't there another matter -- the debt ceiling?

Ah yes, that's the next battle brewing. Remember that time when you maxed out your credit card? That's what the debt limit is all about. The U.S. is on the verge of maxing out its $16.699 trillion credit card. And the president must ask Congress to raise the country's credit limit.

Like the potential shutdown, this is also a Washington-manufactured crisis. And it too is being used for leverage to undermine Obamacare.

But the debt ceiling debacle won't come to a head until October 17. Perhaps it's best to deal with one showdown at a time.

CNN's Leigh Ann Caldwell, Z. Byron Wolf, Adam Aigner-Treworgy, Laura Koran, Lisa Desjardins, Bryan Monroe and Gregory Wallace contributed to this report.