To understand why House Speaker John Boehner has not just ended the government shutdown, now in its fourth day, by standing up to the tea party faction in his caucus, look no further than the highly skewed congressional districts those members represent.

The districts, and their representatives in Congress, are the product of one of the great Republican electoral successes of recent years, the midterm elections of 2010, when the tea party rose to prominence on a wave of antigovernment sentiment, especially opposition to President Obama’s signature health-care law.

Americans reelected President Obama in 2012 and trimmed Republican representation in both houses of Congress – an outcome that he and Democrats took as a national referendum on health-care reform. But the elections also solidified the hold of GOP conservatives on districts whose boundaries were redrawn by victorious Republicans after 2010.

Call it an alternate political universe. The new, bullet-proof GOP districts created voting blocs significantly at variance with the rest of the country, according to data released by David Wasserman, House editor of the Cook Political Report.

The hard-liners now facing off with Speaker Boehner over when and how to end the government shutdown largely are products of these districts.

Exhibit A is freshman Rep. Mark Meadows (R) of North Carolina, a real estate developer who easily won the seat formerly held by three-term Rep. Heath Schuler, a fiscally conservative Democrat who retired in 2012 after the GOP-controlled state legislature changed the district map to favor Republicans.

In August, Congressman Meadows circulated a letter urging Boehner and majority leader Eric Cantor (R) of Virginia to use any fight over the funding of government to insist on the defunding of Obamacare – a strategy proposed earlier in the summer by tea party Sens. Ted Cruz (R) of Texas and Mike Lee (R) of Utah.

The letter picked up 80 House GOP signatures, mainly from tea party-backed members from the South or Midwest. In these 80 districts, Republicans typically trounce Democrats in general elections, but are at constant risk of a challenge from the right.

By contrast, the estimated 20 caucus members now openly backing an end to the government shutdown, without conditions, represent districts where nearly half the voters voted for Obama in 2012.

While Obama defeated Mitt Romney by nearly 4 percentage points in the nation at large, Mr. Romney won by a landslide (23 percentage points) in the House districts represented by the 80 Republican hard-liners, according to an analysis of the Wasserman data by Ryan Lizza, in the New Yorker. Moreover, these lawmakers won their own seats by an average margin of victory of 34 points, he adds.

That’s why national polls signaling that the public is blaming Republicans for the shutdown have, to date, barely made a dent in these lawmakers’ support for a hard-line strategy.

Some 72 percent of Americans disapprove of a government shutdown over the Affordable Care Act, according to a new CBS News poll. Forty-four percent blame the Republicans and 35 percent blame Obama and the Democrats – unchanged from last week, when the poll asked who would be blamed if a shutdown occurred.

When President Clinton and House Republicans shut down government during a clash over spending in 1995 and ‘96, Americans blamed the Republicans by a margin of 2 to 1.

At the time, the public backlash against the shutdown was viewed as a political disaster for Republicans. On Jan. 5, 1996, then-Speaker Newt Gingrich (R) of Georgia broke with the insurgents. He told hard-liners that they had had their say and now it was time to fall in line. Later, he cancelled fundraisers in the districts of several GOP lawmakers who refused to go along.

But Boehner can’t count on that historical context to influence hard-liners in the current shutdown battle. Nearly half of House Republicans were elected since the George W. Bush administration. Only 16 percent of House Republicans were around for the 1995-‘96 Clinton-era shutdowns.

“As a result of both redistricting and a huge sorting-out of voters and seats, today's House Republican Conference bears little resemblance to that of 1995-1996, other than 37 members and the word "shutdown,” writes Cook Political Report’s Wasserman.

Meanwhile, from 17 to 20 House Republicans are publicly urging Boehner to bring a clean stopgap spending bill (a CR or continuing resolution) to the floor that funds the government without conditions or changes to Obamacare, according to whip counts in the Huffington Post.

With the support of 200 Democrats, that would be enough to end the standoff and reopen the federal government.

Boehner pulled similar moves when he turned to Democrats for votes to pass the fiscal cliff deal that ended the last debt-limit crisis on Aug. 1, 2011, aid for the victims of Hurricane Sandy on Jan. 15, and the reauthorization of the violence against women act on Feb. 28 – legislation that most Republicans opposed.

But a break now with the hard-liners on what many see as the defining issue for the GOP-controlled House – their last chance to halt a big role for government in health care – could also mark the end of Boehner’s speakership.

Boehner nearly faced a second vote when he ran to hold his office after the 2012 elections. After speculation that as many as 25 tea party lawmakers were prepared to oust him, the hard-liners came within six votes of denying him a win on the first ballot, often seen as a prelude to a resignation.

In the run-up to the government shutdown, Boehner had been urging the caucus to be patient, to recognize the political realities of a Democrat-controlled Senate and a Democrat in the White House. He proposed forcing the Senate to take a vote on defunding Obamacare, but not to link government funding to a highly improbable win in the Senate.

On Sept. 18, when the hardliners refused to go along, he adopted their strategy as his own.

"We're in a very good spot, we're unified," said Rep. Tom Graves (R) of Georgia, one of the 80, after the GOP caucus meeting.

Many hard-liners, and the outside conservative groups supporting them, predicted then that the Senate and, eventually, the president would be forced by an aroused public opinion – like what they were seeing back in their districts – to go along.

When that didn't happen – and when the consequences of a real government shutdown began to be felt, cracks developed in GOP ranks. So far, the hardliners outnumber the moderates 4 to 1. But moderate leaders say that their strength is growing.

“A lot of people say we’ve got to get a clean CR, but they can’t say so publicly because of their districts,” says Rep. Peter King (R) of New York, a leading moderate.

Of the 80 that signed the Meadows letter, probably about half are dug in too deep to change their views on the issue, he says, adding, “I don’t know what will satisfy these guys.” But as for the others, currently privately expressing concerns about the shutdown strategy, he says, “Sooner or later, they’ll vote for a clean CR.”

The GOP moderates hail from districts that are virtual political bookends of the hard-line caucus, according to the Cook Political Report data. The hard-liners come mainly from the South and rural Midwest, the moderates are mainly from the Northeast. Their districts are more educated and more diverse.

Across the aisle, meanwhile, Boehner's political adversaries see only one way out of the government shutdown and a higher-risk clash over the nation's debt limit: that is, a clean break with the hard-liners.

"Congress has to pass a budget that funds our government with no partisan strings attached," Obama said in Rockville, Md., on Thursday. And the only reason Boehner won't allow that vote is that he doesn't want to "anger the extremists in his party."

Senate majority leader Harry Reid (D) of Nevada was also in no mood to offer face-saving gestures to the embattled GOP leader. “It’s time for my Republican friends to defy their tea party overlords,” he said from the floor of the Senate later in the day.

Responding sharply on Friday, Boehner signaled no distance between his position and that of the hard-liners.

“I was at the White House the other night, and listened to the president some 20 times explain to me why he wasn’t going to negotiate. Sat there and listened to the majority leader in the United States Senate describe to me that he’s not going to talk until we surrender,” he said at a press briefing on Friday.

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“And then this morning, I get the Wall Street Journal out, and it says ‘well we don’t care how long this lasts because we’re winning.’ This isn’t some damn game!”

“The American people don’t want their government shut down and neither do I,” he said, renewing his call for negotiations and further concessions to fix Obamacare.