Even some Republicans behind the plan to use a government shutdown as leverage to defund Obamacare concede the plan is unlikely to halt further implementation of the Affordable Care Act.

The government will shut down Oct. 1, the first day of fiscal 2014, if lawmakers fail to approve additional spending. Needless to say, there is scant evidence that President Obama or congressional Democrats would support budget legislation defunding Obamacare to avoid a government shutdown.

But what if they did, if only to keep the federal government operating? Would that mean that implementation of the Affordable Care Act would come to a standstill?

Interviews with congressional policy aides on both sides of the debate strongly suggest that the answer to that question is "no," absent a sudden change of heart by the presidential about his signature initiative.

Rep. Mark Meadows, R-N.C., a leader behind the defund-or-shutdown strategy in the House, acknowledged this dilemma in an interview with the Washington Examiner. But Meadows views this approach as the best way to at least roll back the law and slow down its implementation that is set to accelerate in January of next year.

"There's a number of items in this particular law that we could put a limit on," Meadows said. "We voted so many times to make sure that we repeal it. If repeal is not going to be a part of it, we need to replace it with something that works and hopefully slow it down."

So, what are the factors that make defunding Obamacare unlikely, even if money for it were stripped out of a budget bill or, more likely, from a Continuing Resolution that would extend government appropriations at present levels?

President Obama » In practical terms, there is no way to stop the cabinet and other executive branch agencies Obama controls from shifting resources and personnel to make up for the loss of "discretionary" funds that would result from a continuing resolution that does not include money for Obamacare. In fact, the administration already has paid for much of Obamacare's implementation with money that was not actually designated for Obamacare.

Discretionary spending » The continuing resolution only deals with annual appropriations. Most Obamacare funding comes from a mandatory spending that is built into the law and doesn't have to be approved by Congress from year to year, in the same way that Medicare and other entitlements are automatically financed. For example, only $13 billion in discretionary spending is due Obamacare in fiscal 2014, according to projections, while $71 billion is due the program in mandatory spending.

Accordingly, a continuing resolution that "defunds" Obamacare would fail to halt the bulk of the program from continuing.

Policy riders » Proponents of defund-or-shutdown accurately point out that Congress could attach a policy rider to the continuing resolution to authorize the curtailment or elimination of mandatory Obamacare spending. Congress has routinely approved policy riders to prohibit federal funds from being spent on abortions. Sen. Ted Cruz, R-Texas, is sponsoring legislation that would do just that with Obamacare. His bill includes language that would block all discretionary and mandatory Obamacare spending and prevent any other funds from being used for the law.

However, even fans of the policy rider admit that there is nothing preventing Obama from selectively enforcing such a directive, or finding a way around it, similar to how he decided to delay implementation of Obamacare's employer mandate despite the fact that there is no language in the Affordable Care Act that gives him the authority to do so.

Defund vs. repeal » Defunding Obamacare doesn't equal repealing it. Even assuming the continuing resolution ran for a full year, which is unlikely, proponents of the strategy would have to engage in the defund fight all over again, unless Obama and the Democrats chose to permanently stand down and abandon the law, even as it remained on the books. Given their strong opposition to repeal despite Obamacare's lousy poll numbers, this appears improbable.

Outside groups » Various nonprofits are at work right now on various aspects of implementation. In particular, these groups are active in trying to encourage Americans to sign up for Obamacare-subsidized health care and to enroll in the exchanges that offer these insurance policies. Unless there are no exchanges, these third-party activities are likely to continue.

Sen. Richard Burr, R-N.C., has cosponsored the Cruz bill, but opposes the defund-or-shutdown strategy because he does not believe it will accomplish the goal of stopping Obamacare. His reasoning is simple and probably unassailable: He doesn't expect the president to play along.

"This administration has already proven with the Affordable Care Act, they've found ways to get around the law to accomplish what they want," Burr said.