The House Republican plan being advanced by Speaker Paul Ryan has been criticized by many conservatives for not going far enough in removing Obamacare's regulations requiring that insurance policies cover a certain list of government-mandated benefits.

But sources inside Senate leadership indicated to the Washington Examiner that the House bill should not be seen as the final say on the matter, and that there are ongoing efforts by Senate lawyers to test whether Republicans can move more aggressively against the regulations under the arcane Senate procedure known as reconciliation, which allows legislation to pass with a simple majority.

"We're going to try to win the debate on all of them," a senior leadership aide said of regulations. "It's our desire, at the end of the day, to get everything in there that we could possibly get past the goalkeeper."

Another senior leadership aide cautioned, however, that the possibility that the regulatory structure could be fully stripped from Obamacare with a simple majority was still a "long shot."

At issue are the "essential health benefits" within Obamacare, which require that all insurance policies include a set of benefits such as preventive medicine and maternity care. Though they make health policies more comprehensive, they also make them more expensive, and leave fewer options for individuals with lighter medical needs who are searching for cheaper insurance. This has complicated efforts of Republicans, who have pledged to lower premiums and increase choice in their replacement package.

The fact that House Republicans kept these regulations in place also contributed to the rough score the GOP received from the Congressional Budget Office, because the plan would offer less generous subsidies than Obamacare without doing enough to bring down the cost of insurance.

Conservatives Sen. Ted Cruz and Rep. Mark Meadows, in an op-ed for the Wall Street Journal, urged Republicans to repeal all the regulations, and dismissed arguments saying that Senate procedure makes this impossible.

Among the tests that govern the use of the reconciliation procedure in the Senate is the requirement that any provision must have a budgetary impact and that the impact cannot be merely "incidental."

Obamacare drives up the cost of premiums, and as the CBO reminded everybody in its analysis, when premiums go up, so do Obamacare's subsidies (which means more federal spending). So while it's undeniable that the regulations have a budgetary impact, the matter does not end there, and there's a bigger debate over whether that impact should be considered incidental. Democrats would argue, among other things, that the primary purpose is to make sure that policies cover certain types of care, and thus it shouldn't be considered budgetary for the purposes of the rule.

Media accounts of reconciliation often describe a process in which this is all litigated on the Senate floor when the bill is presented, with the parliamentarian advising the majority as to what is in order on the spot. But Senate leadership sources describe a process that actually is ongoing, in which lawyers for Republicans and Democrats argue with each other behind closed doors for hours, in front of the Senate parliamentarian, to get a sense of what she thinks passes muster. That could lead Republicans to abandon certain ideas, or to tweak how a law is drafted to try to make sure it complies with the rules. Ideally, leadership would want to avoid any surprises on the floor.

The essential health benefits are going to be a part of these ongoing debates.

"Our counsels are preparing memos and they're trying to draft language to make the argument that these are budgetary and that we should be allowed to do them," said one of the leadership aides. "We're not there yet, and I don't know if we'll get there. But the effort is underway."

Of the House bill, the aide said, the important thing is that it doesn't have any elements that prevent it from being considered in the Senate under reconciliation in the first place, at which point it could always be amended. "I think they've done everything that certainly that they think that they can do, but because there's no way to settle these issues until you actually get to the Senate, there may be other things that we can do over here and if we can they'll be happy to accept those changes," the aide said.

Of course, even if Republicans could get over the procedural hurdle allowing them to remove the benefit mandates through reconciliation in theory, it is far from certain that they could win over the 51 votes needed to scrap the regulations.