Bitter infighting between centrists and die-hard conservatives has shaken the US Republican Party to its core, leading to a bruising battle that played a critical role in the government shutdown.
The Republican leadership was sparring with President Barack Obama and his Democrats over a path forward on funding government, but they were also fending off a challenge by a band of Tea Party Republicans hell-bent on unravelling Obama's health care law.
With Democrats holding the White House and the Senate, many conservatives concluded they needed to hold their ground in the Republican-controlled House of Representatives, or risk getting steamrolled by Obama's agenda.
In recent weeks, as the clock ticked toward the end of the fiscal year on September 30, the die-hard conservatives made their stand: defund or delay so-called "Obamacare," at virtually any cost.
The Tea Party faction includes 50-odd House conservatives who have largely thumbed their nose at the Republican establishment and camped out on the far right of party doctrine.
But behind closed doors they swing a big stick, leaning heavily on party leaders. They are often in opposition to mainstream Republicans on key votes.
They have been accused of stalling once-in-a-generation immigration legislation in the House, after it passed with bipartisan support in the Senate.
Many of them were swept into office in the 2010 election, following passage of the health care law, which they derided as socialized medicine. Constituents elected them as a counterweight to centrist -- and, in their view, ineffectual -- Republicans.
At the center of the storm is House Speaker John Boehner, the mostly-unruffled party leader whose style is at odds with the rebellious heart-on-their-sleeve ideology of the Tea Party.
Boehner was first elected to Congress in 1990, patiently climbing through the ranks to finally earn the Republican leadership mantle in January 2011.
Since then he has struggled to keep the right-wing faction at bay as he engaged in one fiscal standoff after another with the president.
Boehner was routinely criticized for his weak hold on the caucus, even for being "held hostage" by the far-right in such negotiations.
In the run up to the October 1 budget deadline, Boehner said he wanted to pass a stopgap government funding measure without any firm anti-Obamacare conditions attached.
But the strategy imploded thanks to a revolt by the Tea Party faction, who essentially forced Boehner to link Obamacare's defunding or delay to the spending bill.
Boehner agreed, neither Republicans nor Democrats blinked, and the government lurched into shutdown.
This past week's strategy has backfired so far, with several Republicans blaming the hard right for causing the shutdown and openly worrying that the legislative approach could harm the party's chances in next year's elections.
"It was never realistic to tie Obamacare to" government funding, Republican Senator Jeff Flake told AFP, expressing concern over possible lasting damage to the party brand.
"I don't think it ends well for us."
Regardless of Republicans' near-universal desire to repeal Obamacare, tensions within the party ranks soared over the strategy of pushing government to the brink over opposition to the health law.
On Monday, hours before the shutdown was to begin, Republican lawmaker Devin Nunes pulled no punches, describing his colleagues who were willing to force a shutdown over Obamacare as "lemmings with suicide vests."
Republican Senator Bob Corker has also berated Tea Party senators for their positions.
"I think Speaker Boehner has a tough job," said Corker.
"Box canyons weaken us and we need to unite, we need to use our heads and we need to pull together."
Tim Huelskamp, a second-term Tea Party Republican who once earned a rebuke from Boehner for his excessive criticism of leadership, dismissed the suggestion that the speaker was under the thumb of the hard-right.
"He's been held hostage by 225 members," Huelskamp said, referring to the overwhelming majority of House Republicans who voted Monday to delay Obamacare.
"At the end of the day it's pretty hard to go home, particularly in a Republican primary, and say 'Hey, I just let (Democratic Senate leader) Harry Reid get his way.'"