House Speaker John A. Boehner (R-Ohio) has a long and difficult weekend ahead .

With only three days in which to avert a partial shutdown of the federal government, the Republican leader’s new task is as familiar as it is excruciating: uniting an unruly GOP conference behind a plan to keep the government running.

It’s the same predicament Boehner was in a week and a half ago, before conservative members practically forced him to hold a vote on a stopgap spending measure that would defund President Obama’s signature health-care law. Predictably, the Democratic-controlled Senate stripped out the health-care provision Friday, returning to the House a bill that Boehner says he will not accept.

What he will agree to, and what he can convince his colleagues to support, is the big question. House GOP leaders have not signaled what changes they intend to make to the bill, known as a continuing resolution. Already, conservatives have scuttled plans by leadership to move the fight over the health-care law they call “Obamacare” to next month’s battle over the White House’s request to raise the nation’s borrowing limit. They’ve also thwarted efforts to hold a vote on the debt ceiling before the stopgap spending showdown is settled.

Boehner will huddle with his conference at noon Saturday in the basement of the Capitol. What happens next will depend on what he hears.

A numerical take on the possible outcomes of the looming government shutdown. (Sandi Moynihan and Lisa Rein/The Washington Post)

But here’s how bleak things look for the speaker: Even if he cajoles his conference to agree on a new spending bill in time to avert a shutdown, Senate Democrats will kill anything that threatens Obamacare and reject anything resembling conservative demands.

“We’re not going to be extorted,” Senate Majority Leader Harry M. Reid (D-Nev.) told reporters Friday. “The country’s not going to be extorted. We’re not going to negotiate with a gun to our heads.”

It’s hard enough for Boehner and his deputies to round up votes under normal circumstances. Now, he’s competing for attention with Sen. Ted Cruz (R-Tex.), a fiery conservative freshman who delivered a 21-hour address in opposition to the health-care law this week.

National Review reported Friday that Cruz had urged a group of House conservatives to defy Boehner by opposing a proposal by GOP leaders to use the debt ceiling talks as the main vehicle for pushing their demands. Democrats, meanwhile, are urging Boehner to accept the Senate-passed bill and move on.

“Over the next three days, House Republicans will have to decide whether to join the Senate and keep the government open or shut it down because they can’t get their way on an issue that has nothing to do with the deficit,” Obama said Friday at the White House.

If Boehner were to try to pass the Senate bill with the support of moderate Republicans and Democrats, he’d face a level of fury from many House Republicans that would make their current stubbornness seem mild.

Responding to Obama’s statement Friday afternoon, aides to Boehner said the speaker hasn’t spoken with the president at all this week.

As for what Obama had to say, Boehner spokesman Brendan Buck said in an e-mail: “The House will take action that reflects the fundamental fact that Americans don’t want a government shutdown and they don’t want the train wreck that is Obamacare. Grandstanding from the president, who refuses to even be a part of the process, won’t bring Congress any closer to a resolution.”

There are a lot of difficult questions for Boehner, and no easy answers. No matter what path he chooses, he will make somebody very unhappy.

If he’s able to navigate his way out of a government shutdown, Boehner will barely have time to catch his breath before he will be in another standoff, over the nation’s borrowing authority. The nation will reach its borrowing capacity on Oct. 17, according the Treasury.

Obama is demanding that Congress send him a debt limit resolution with no strings attached. He has said repeatedly that he won’t negotiate on that posture. But no matter what happens with the continuing resolution negotiations, House Republicans are not expected to bend to the president’s wishes.

But first, the short-term budget standoff must be resolved.

“We’re saying to Speaker Boehner, like that old quote from ‘Field of Dreams,’ listen to the voices telling you to pass this bill. Ease your pain,” Sen. Charles E. Schumer (D-N.Y.) pleaded Friday. “Put this bill on the floor. It’ll pass. And then you can move on to the next issue.”

The problem for Boehner, though, is that throughout the course of his speakership, the “next issue” has consistently proven to be as painful as the last one.

Ed O’Keefe contributed to this report.