On Friday, the House passed a measure that would keep the government running through mid-December. But it came with what Democrats consider a poison pill: It defunds President Obama’s signature health-care law, known as Obamacare. There is no way whatsoever — think pigs flying — that the Senate will agree to the House plan. Senate Majority Leader Harry M. Reid (D-Nev.) said the House bill was “dead,” then for emphasis added: “Dead.” ¶ That sets up eight days of brinkmanship between the Republican House and the Democratic Senate and White House, leading to midnight Sept. 30, when much of the government will shut down if there’s no deal. ¶ Leaders on Capitol Hill expect the face-off to go right up to the deadline, if not beyond. Below is a day-by-day look at how it’s all likely to play out — with the caveat that events can change quickly.

Monday: The Senate will convene briefly, with just a few members on hand. Reid is expected to call up the House bill, known as a continuing resolution, and file a motion that sets up initial votes on the measure. Under Senate rules, there will be two votes just to determine whether the chamber gets to a vote on final passage of the bill. These are the “cloture” votes, which require 60 ayes to choke off a filibuster; Reid will file a motion one day, then there must be an intervening day of debate, then the filibuster-busting vote comes. Reid will file the first of these Monday, setting up a vote Wednesday.

The House is not in session.

Tuesday: The full Senate will return just before noon. After approving some noncontroversial judicial nominees, Republicans and Democrats will go to their separate weekly lunches to hash out strategy. At about 2 p.m., Reid and Minority Leader Mitch McConnell (R-Ky.) will hold back-to-back news conferences where they will probably call each other names. The Senate will continue debating whether to cut off debate on the continuing resolution.

Deadlines and showdowns won't make Capitol Hill a fun place to be this fall. (The Washington Post)

The House is still not in session.

Wednesday: The Senate’s first filibuster vote will probably take place in the late morning, and the chamber is almost certain to vote to proceed. The rules then call for 30 more hours of debate on the motion to proceed before senators can start debating the actual bill. (It’s possible, though not expected, that Republicans could waive the 30 hours.)

The House will return. Around 4:30 p.m., Speaker John A. Boehner (R-Ohio) will probably huddle with his leadership team to plot strategy. At 6:30 p.m., the full House will convene for some noncontroversial votes.

Thursday: At 9 a.m., House Republicans will gather in the Capitol basement for their weekly policy huddle. Boehner’s leadership team usually holds a news conference afterward, around 10 a.m. The big issue for House leaders will be determining whether they have enough support for a bill to raise the nation’s debt limit. That deadline will come in mid-October, but it is relevant to the shutdown debate because it provides another chance to try to defund Obamacare. (More on that later.)

Reid’s Senate leadership team usually hosts its weekly news conference at noon. If tradition holds, Reid will call Boehner a bunch of names.

At some point Thursday afternoon or evening, the 30 hours of debate in the Senate will expire, and senators are likely to pass the motion that formally begins debate on the bill. Simultaneously, Reid will file a second motion setting up the next vote to try to stop the last filibuster attempt by Sen. Ted Cruz (R-Tex.) and other Obamacare opponents. They will then have until Saturday to make their final stand to persuade enough GOP colleagues to filibuster the legislation.

Friday: The House could pass a bill to raise the debt ceiling. An initial draft of the legislation contains something for everyone in the Republican Conference: It increases the debt limit until the end of 2014, delays Obamacare for a year and includes a grab bag of conservative goals, such as offshore drilling, Medicare means testing, a tax code overhaul and approval of the Keystone pipeline. The bill is designed to gain the necessary bare majority with GOP votes alone. But there’s no guarantee of that, because a significant number of House Republicans don’t believe in raising the debt limit under any circumstances.

In the Senate, this is the intervening day of debate on the last filibuster vote. Cruz and Sen. Mike Lee (R-Utah), his conservative ally in this fight, have vowed to use any means necessary to try to hold up the continuing resolution. They may even launch into an old-fashioned talking filibuster, taking to the floor for hours at a time. These are rare in the modern Senate, since new rules have allowed the minority to block legislation with 41 votes, if it can hold together. A talking filibuster would be largely theatrical; Cruz and Lee won’t be able to stop the bill, because parliamentary procedures will have locked in the votes that are set to occur.

Saturday: The final filibuster-vote day in the Senate. One hour after senators convene, they will hold a vote that, if it receives 60 ayes, will end any filibuster attempt and lock in a time for a final vote on the bill. This is the point when things will get weird.

At this time, the continuing resolution will still have the exact language conservatives love — they begged Boehner to pass it, in fact — but Cruz and Lee will be opposing the bill for strategic reasons. That’s because once the measure clears this last 60-vote hurdle, Reid will call up his amendment to strip out the portion that defunds Obamacare. Having already avoided a filibuster, he’ll just need a simple majority to pass his amendment, then a simple majority to approve the new bill and send it back to the House. So the only recourse for conservatives is to try to preemptively filibuster their own bill, stopping it from coming to a vote. A vote to do that is, in effect, a vote to shut down the government, because the bill is the only vehicle to fund it. For that reason, it’s not likely that many Senate Republicans will go along with Cruz.

Sunday: By Sunday morning, Reid will have brought up his amendment to remove the health-care language from the bill. Final passage could come around dinnertime. The bill will then go across the Capitol to the House, with a countdown clock of roughly 30 hours until government funding expires.

Monday, Sept. 30: Boehner faces a momentous decision: He can either call a vote on the Senate bill that includes funding for the health-care law, or he can try to attach something else to it that gains a majority so he can send the bill back to the Senate as the deadline looms. At this point, it’s unclear what would be attached to the legislation and whether 218 Republicans would support it. Boehner could try a poison pill other than defunding Obamacare, but many Republicans may oppose it because a vote for it would be a vote for funding the health-care law.

If Boehner does go this route, and if he gets the votes, there will almost certainly be a shutdown.

If not, the question will be whether House leaders can get enough Republicans to join Democrats to pass the Senate bill and keep the government running.

This is where the debt-ceiling bill comes into play. House GOP leaders could argue to their caucus that they could use the October debt-limit deadline to take up the effort to defund the health-care law and avoid a painful shutdown in the meantime. Again, it’s entirely unclear whether enough Republicans would go along. If not, the government would shut down.