Now—when the House considers the bill to fund government for the rest of the year and seeks to reduce spending by $100 billion—is the best of all times to defund Obamacare. But although it’s a golden opportunity, so far defunding Obamacare is not on the agenda.

Republican freshmen have the chance to fix that if they stand firm again as they did last week.

House Republicans say they are crafting a bill to save taxpayers $100 billion. Their revised proposal would rescind funding for 123 different federal programs and would lower future funding for many others. Yet it leaves Obamacare unscathed. Except for transferring $750 million to a different public health program, the tens of billions appropriated last year for Obamacare would remain available for the White House to spend freely.

Only if House leaders expressly permit it can an amendment be offered successfully on the House floor. Otherwise, Members like Representative Steve King (R–IA) may be boxed out by House rules that disallow amendments that try to go back and reclaim money spent by last year’s Congress.

Yet that’s what the bill does to other programs! A different standard is being applied to permit the 123 other reachbacks that were approved by the Appropriations Committee—but not for defunding Obamacare.

So now will conservative House Members—especially the GOP freshmen—once again play hardball with party leaders and oppose any measure that does not permit defunding Obamacare? That would be a repeat from last week, when they forced the Appropriations Committee to propose more spending cuts than originally approved.

Certainly Obamacare is also a much better target for rescissions than the defense budget, which finds itself on the chopping block even in the midst of a hot war.

Even now, many conservatives say the bill falls $16 billion short of the GOP commitment to make $100 billion in spending cuts this year. The House Republican Study Committee, led by Representative Jim Jordan (R–OH), plans to offer an amendment to cut that elusive $16 billion. These extra savings could come from Obamacare—but only if House leaders choose to permit it.

Some don’t realize that last year’s Congress did fund Obamacare even though it failed to pass appropriations bills for anything else. The billions given to Obamacare are outlined in Congressional Research Service Report R41301, “Appropriations and Fund Transfers in the Patient Protection and Affordable Care Act (PPACA),” issued last October 14.

This includes major money that could be pulled back immediately. Congress could rescind the $5 billion appropriated in Section 1101(g) to create high-risk pools, the $5 billion appropriated in Section 1102(e) for a re-insurance program, and the $6 billion in Section 1322(g) to create insurance exchanges. The CRS report details billions more in current and future funding equally available for cutting.

That’s a dirty little secret about the new law. As further detailed in a Heritage Foundation report, rather than respecting the right of future Congresses to decide on funding, Obamacare’s sponsors included several years worth of current and future appropriations for the health care makeover—money that mostly has not yet been spent.

Despite the recent court ruling that the new health law is unconstitutional, the White House insists it will go charge forward to implement the law and spend that dough.

Defunding Obamacare is a two-fer. It responds to the public mandate for repeal, plus it moves the House GOP closer to fulfilling its pledge to cut spending by $100 billion this year.

The House will never have a better chance to stop it than to defund Obamacare this week—before it’s too late.