Establishment Republicans, led by House Speaker John Boehner, want to go into negotiations with Democrats at the end of this month with a chance of actually passing a budget. Tea Party Republicans, however, are pursuing a scorched earth strategy that calls for no budget unless the Affordable Care Act is defunded.
President Obama, of course, isn't likely to dismantle the most important feather in his legislative cap, leaving a government shutdown a real possibility.
The Tea Party won a small victory this week by convincing House Republicans to vote on a bill that would simultaneously fund the government and defund ObamaCare. While no decisions have been made on the vote, it shows that the Tea Party's influence is something that can't be ignored.
What is at the crux of this Republican civil war? As Ezra Klein puts it in The Washington Post, "It would be a disaster for the party to shut down the government over ObamaCare … But it's good for every individual Republican politician to support shutting down the government over ObamaCare."
One reason it's "good" for individual Republicans to support the bill is because, as The New York Times reports, conservative groups are "raising and spending millions" to defeat it. So who, exactly, is funding the push to defund ObamaCare?
Club for Growth
The group, according to The Washington Post, is a "conservative campaign-finance machine" that helped elect 13 conservative House members and bring down two moderate veterans of the Senate.
"Every Republican ran on defunding or repealing ObamaCare," Chris Chocola, president of the Club for Growth, told the Post. "This is a test of whether they’re actually going to do what they say they’re for"
Those aren't just words. The conservative anti-tax group is targeting Rep. Aaron Schock (R-Ill.) in next year's primary election, according to Times, because he voted to increase the debt ceiling in 2011 and for a stopgap spending bill in 2012 to keep the government running — all without demanding that ObamaCare be defunded.

Senate Conservatives Fund
Want to know who signed an anti-ObamaCare pledge written up by Sen. Mike Lee (R-Utah)? The Senate Conservatives Fund, self-described as a "grassroots organization dedicated to electing strong conservative leaders" and not "liberal Republicans," makes it easy to find out with its Senate Republican Whip List.
The group, which started out as Jim DeMint's political action committee in 2008, is now stepping into the House battle with a new expansion: The House Conservative Project, which it hopes to use to beat ObamaCare in the House and build a "a farm team for the Senate," as its executive director, Matt Hoskins, tells TPM.
The National Liberty Federation
As David Weigel puts it in Slate, "We don't have the financial reports yet, but later this year we'll learn just how much money was raised — and how much was actually spent, against Republicans — by conservatives working on something that the party leadership knew could never pass."
One of those groups raising money to defeat ObamaCare: The National Liberty Federation, which started out as the South Florida Tea Party before changing its name over "branding" concerns.

Tea Party Patriots
Conservative groups aren't just working behind the scenes to defeat ObamaCare. The Tea Party Patriots, along with For America and Freedomworks, held a 10-city tour with the message "Exempt America," complete with speakers like Sen. Ted Cruz (R-Texas):
Heritage Action for America
The political arm of the Heritage Foundation has "spent more money so far on attack ads this year against House and Senate Republicans than the Democratic Senatorial Campaign Committee, Democratic Congressional Campaign Committee and Democratic National Committee, combined," writes Republican strategist Brian Walsh in U.S. News & World Report.
Aside from funding attack ads, Heritage Action also keeps a conservative scorecard and publishes articles like this one, which says Americans are willing to risk a government shutdown if it means Congress is fighting ObamaCare.