How difficult would it be to repeal Obamacare for good?

If the leading Republican candidates agree on one thing, it’s doing away with Obamacare.

“The one thing we have to do is repeal and replace Obamacare,” Donald Trump has written on his campaign website, while Marco Rubio has outlined his plan to “Repeal Obamacare” and “replace it with a 21st century, market-driven alternative.” Likewise, Senator Ted Cruz emphatically declared during the February 25 GOP debate that “As president, I will repeal every word of Obamacare.”

Is this the bombastic rhetoric of candidates trying to fire up their base? Or would Republicans actually be able to repeal Obamacare under a Republican president?

In short: yes, they could. But it wouldn’t be easy.

The main GOP obstacle

The essential requirement to achieve repeal is Republican control of the White House, the U.S. Senate and the House of Representatives in January 2017.

Unless both houses of Congress and the executive branch are under GOP control, Democrats would be able to block any repeal effort – and the Obamacare trench warfare that’s taken place since Democrats lost control of Congress in January 2011 would continue.

But even if Republicans control Congress and the White House, Senate Democrats could filibuster any legislation that repeals Obamacare.

Sixty senators must vote to close a filibuster – a Senate parliamentary tool designed to protect the rights of senators to slow or stall legislation and other matters. While, historically, filibusters took the form of long speeches on the Senate floor, these days it’s a less heroic procedural maneuver.

It’s unlikely that Republicans will have a 60-vote majority in the Senate in 2017. Meanwhile, Senate Democrats have been unanimous against repeal, and the number of Democrats in the chamber next year is predicted to increase over their current 46.

For this reason, even in if they’re in the minority, Democrats could block any straight repeal legislation and compel Republicans to resort to another path.

Skirting the filibuster with reconciliation

Republicans could then initiate an arcane legislative process called budget reconciliation. Invented in 1974 by the late West Virginia Senator Robert Byrd (arguably the shrewdest legislative tactician ever), budget reconciliation is a special legislative process that enables federal budget bills to be approved in an expedited fashion.

The advantage of reconciliation is that it permits a bill to be approved by 51 votes. (If Republicans hold 50 votes in the new Senate – a possibility – a Republican vice president can provide the 51st vote.)

Since reconciliation bills cannot be filibustered, any Obamacare repeal bill done using reconciliation wouldn’t need a 60-vote majority to proceed. And debate on a reconciliation bill is limited to 20 hours. For a frustrated Senate that doesn’t have a 60-plus vote filibuster-proof majority, it’s the most potent legislative shortcut imaginable.

But there’s a vital catch: any item in a reconciliation bill must have a measurable, direct impact on federal spending, up or down.

The individual who decides what legislative items do and do not conform to this rule is the Senate parliamentarian – the individual tasked with advising Senate leaders on the interpretation of Senate rules. Appointed by the Senate majority leader whenever the prior parliamentarian steps down, a former Senate librarian clerk named Elizabeth MacDonough currently holds the position.

A full ACA repeal bill would be deemed noncompliant by MacDonough and set aside because so many of its individual provisions do not have a significant budget impact. In a process known as the “Byrd bath,” Senators can challenge any entire bill, section, subsection, paragraph, sentence or word as “out of order,” meaning there is no significant budget impact. Items eliminated by the parliamentarian – called “Byrd droppings” – are removed from the bill.

But could Republicans then devise a partial – and critically damaging – ACA repeal bill that might pass muster with MacDonough or her successor?

Yes, they can. In fact, they’ve already done so.