President Barack Obama (R) shakes hands with Speaker of the House John Boehner (R-OH) during a meeting with bipartisan group of congressional leaders in the Roosevelt Room of the White House on November 16, 2012 in Washington, DC. Obama and congressional leaders of both parties are meeting to reportedly discuss deficit reduction before the tax increases and automatic spending cuts go into affect in the new year. (Photo by Olivier Douliery-Pool/Getty Images)

You’ve heard it all before: President Obama accusing Republicans of threatening to wreck the economy, Republicans arguing they are determined to cut spending and end “Obamacare,” endless stories about a government shutdown or default, ticking clocks on cable news networks.

But this time is different. In 2011 and earlier this year, the White House and congressional Republicans negotiated hard but ultimately reached agreements on funding the government and increasing the debt ceiling. Now, officials in both parties say a government shutdown is possible and perhaps even likely next week, as current funding expires on Sept 30. Here’s why:

1. The Republicans are determined to block Obamacare before it starts

Many of the benefits of the president’s signature health care law have long been implemented, such as a provision that allows parents to keep their children on the family’s health insurance plan until the child turns 27. But on Oct. 1, Americans can begin to enroll in subsidized health insurance plans and expanded Medicaid programs under the law.  Some conservatives argue that process will lead to massive cost increases for the federal government. Others fear that once Americans start getting low-cost health benefits, it will be impossible to ever repeal “Obamacare.”

Either way, as Sen. Mike Lee (R-Utah), said recently of Obamacare, “this is our last, best chance to stop this disaster.”

So limiting Obamacare is the main goal of the Republicans over the next month, and they are more determined than ever to succeed. They are pushing a long-shot proposal to defund the law as a part of a government funding bill. House Republicans are also likely to advance a provision that would delay the law’s implementation for a year in exchange for increasing the debt ceiling. Democrats strongly oppose both ideas.

2. Obama has little to lose from a government shutdown

In 2011, the White House was wary of a shutdown, in part because it would be unhelpful for a president standing for reelection a year later and trying to project an image as an effective manager of an increasingly-partisan Washington. Earlier this year, when Obama avoided an impasse over both the debt ceiling and reached a compromise with Republicans that raised taxes on the wealthy, but not as much as some Democrats would have liked, the president was still trying to maintain relationships with GOP, hoping to get Republicans on board with gun control and other parts of his agenda.

Almost 10 months into Obama’s second term, it’s now clear the Republicans no intention to join with the president on any major issues. In turn, he has little incentive to work with them, particularly as their principal goal seems to be weakening Obamacare.  If a government funding bill is tied to a provision limiting the health care law, Obama sounds like he will accept a temporary government shutdown, blame Republicans for the impasse and hope that political pressure forces them to drop their demands. White House officials believe the economy can survive a temporary government shutdown, even as they warn of the more dire effects that would result from exceeding the debt limit.

“This is an interesting thing to ponder, that your top agenda is making sure 20 million people don’t have health insurance.  And you’d be willing to shut down the government and potentially default for the first time in United States history because it bothers you so much that we’re actually going to make sure that everybody has affordable health care,” Obama said in a speech at the Congressional Black Caucus Foundation’s annual dinner on Saturday. “Let me say as clearly as I can:  It is not going to happen.”

3. Tea Party Republicans have little to lose from a shutdown

The comments by Sen. John McCain (R-Ariz.), Sen. Bob Corker (R-Tenn.) and other more moderate Republicans that it would be unwise for the GOP to threaten a government shutdown over Obamacare are irrelevant. The true drivers of this debate are rank and file House Republicans. Many of them are strongly conservative, won elections in 2010 and 2012 under the “Tea Party” mantle and came to Washington determined to to block or reverse President Obama’s agenda, including the health care law.

It may be bad politics for the Republican Party overall to be blamed for a government shutdown. But individual House Republicans won’t suffer from a shutdown; their conservative constituents will praise them for standing up to Obama. This is why Republican Party leaders like Speaker John Boehner have so little influence right now. For some Republicans in the House, the continued existence of Obamacare is something they cannot abide. And a shutdown that leads to a broader debate about the health care law is exactly what they want.