Following last week’s Supreme Court decision upholding the Patient Protection and Affordable Care Act, or “Obamacare” as some refer to it, Mitt Romney said “What the Court did not do on its last day in session,” adding, “I will do on my first day if elected President of the United States. And that is I will act to repeal Obamacare.” He doubled down on the rhetoric in a new campaign ad (video below) with the slogan, “Day one. Job one. Repeal Obamacare.”

Will F. from Lexington, Ky. writes in with the following question:

If Mitt Romney is elected, would he have the power to repeal the health care law as he claims? If not, what other options does he have to push repeal and what are the chances of it, especially given he pushed a similar health care law in Massachusetts?

Brookings Institution senior fellow Sarah Binder answers:

Actual repeal of health care reform on “day one” of a Romney administration is not possible, but a President Romney—assisted by a Republican House and Senate—could put into motion the steps necessary to pursue repeal over the course of 2013. Technically, Romney’s success would depend on whether or not Republicans gain control of both the House and Senate and on the byzantine rules of the budget process in Congress. Politically, Romney’s success would probably depend on acting swiftly before all of the law’s most popular benefits kick in in 2014. Let’s take each of these in turn.

Absent unified Republican party control of Congress and the White House after the November elections, a newly-elected Romney would have no chance of repealing the health care law. Even if Republicans hold the House, a Democratic Senate would be unwilling to support repeal. And even if Republicans win control of the Senate, without a sixty-vote majority, Senate Republicans would be limited in what they could achieve given the rules of the Senate. In the House, the rules allow a simple majority to work its will, so repeal would be easy. But in the Senate, the rules require a sixty-vote majority to defeat a filibuster. (That is why a sixty-vote Democrat majority in 2009 was able to move much of the health care bill into law over the objections of every Republican senator.) But in 2013, Democrats would be unlikely to cross the aisle to offer votes to repeal the landmark law.

Still, Congressional budget rules offer a path to repeal for a Republican majority with fewer than sixty votes in its own ranks. The key to repeal would be the budget process known as “reconciliation.” If Congress passes a budget resolution in 2013 and includes within it provisions known as “reconciliation instructions,” a reconciliation bill would offer a legislative vehicle for repealing at least some of the provisions of the law. Reconciliation thus becomes the key to Romney and the Republicans’ success in the Senate, since it requires only 51 votes to pass. (Because Republican would first have to pass a budget resolution, the earliest we’d see repeal in the Senate would be closer to the Spring of 2013.)

But this is the Senate: Nothing is ever so easy. Aghast at majorities’ exploitation of reconciliation, the late Senator Robert Byrd (D-West Virginia) in the mid 1980s pushed the Senate to adopt the “Byrd Rule,” a rule that places tough limits on what majorities can include in a reconciliation bill. In short, the Byrd Rule prevents majorities from including provisions in reconciliation that are “extraneous” to budget targets — unless proponents can muster sixty votes to waive a Byrd Rule challenge or to reject a point of order under the rule. “Extraneous” generally refers to provisions that do not produce a change in spending or revenues, although there are actually six definitions of “extraneous” in the Budget Act (including one that prevents inclusion of measures that would increase the deficit for a fiscal year beyond those covered by the reconciliation bill).

Why does this byzantine Byrd Rule matter for the prospects of repeal? Not every provision of the health care law (such as the individual mandate) directly affects federal spending or revenues. Moreover, the original health care law was judged by the Congressional Budget Office to save nearly $300 billion. If the Democrats could successfully charge that Republicans have violated the Byrd Rule in their reconciliation bill, Republicans would lack the sixty votes necessary to overcome Democrats’ objections under the rule. Of course, we don’t know which provisions the Senate parliamentarian could judge to be in violation of the Byrd Rule, and so we don’t know for sure how successful a Republican repeal effort would be. The devil, as always, is in the details. To be sure, Republicans could replace the parliamentarian with an umpire who gives more favorable rulings about the Byrd Rule, making it easier for Republicans to avoid Democrats’ challenges. Although there is precedent for such a move, even some Republicans might balk at such institutional gusto.

So, assuming a Republican Congress under President Romney were to judge repeal to be politically feasible, then a road to at least partial repeal would technically be possible in the Senate. But it would be a bumpy and it might hit some dead-ends, thanks to the legacy of Senator Byrd.

Send your own think tank question with your first name, last initial and your city to