10/27/2012 03:35 pm ET Updated Dec 27, 2012

Romney and Roe

We are coming up in January on the 40th anniversary of the Supreme Court's decision in Roe v. Wade. What are the chances that the Supreme Court will overrule Roe if Mitt Romney is elected president?

A reasonable guess at present, based on past performance, is that five of the current justices (Breyer, Ginsburg, Kagan, Kennedy and Sotomayor) would vote to reaffirm Roe, and four of the current justices (Roberts, Alito, Scalia, and Thomas) would vote to overrule Roe.

Thus, for Roe to be overruled, Romney, if elected, would have to have the opportunity to replace at least one of the five justices who support Roe. Based on the life expectancies of those five justices and on past experience, there is at least a 50 percent chance that at least one of those five justices will leave the Court in the next four years.

That does not mean, however, that there is a 50 percent chance that Romney's election will result in Roe being overruled. This is so because not every justice appointed by presidents committed to overruling Roe actually votes to do so. In the years since Roe, three Republican presidents who were clearly opposed to Roe have appointed seven justices to the Supreme Court. President Reagan appointed Justices O'Connor, Scalia and Kennedy; President H.W. Bush appointed Justices Souter and Thomas; and President George W. Bush appointed Chief Justice Roberts and Justice Alito.

Of those seven justices, three failed to vote to overrule Roe. Although they may have questioned the wisdom of Roe, they nonetheless concluded that respect for precedent required them to adhere to Roe. In so doing, they narrowed the scope of Roe in some significant respects, but they reaffirmed the core holding that a woman has a constitutional right to terminate an unwanted pregnancy, subject to reasonable regulation by the state.

Of the other four justices appointed by presidents committed to overruling Roe, two -- Scalia and Thomas -- have already voted unequivocally to overrule Roe. The other two -- Roberts and Alito -- have not yet had occasion to address that question directly. But given their general approach to precedent (they are stunningly quick to overrule prior decisions if they disagree with them), and their hostile approach to abortion-related issues generally, it is virtually certain that they will join Scalia and Thomas in voting to overrule Roe, if given the opportunity to do so.

Thus, if Romney is elected and gets to appoint a justice to replace one of the five justices who currently support Roe, there is roughly a 60 percent probability that that new justice will vote to overrule Roe. If we put these two numbers together, it is reasonable to predict that if Romney is elected there is a 30 percent chance that the Court will vote to overrule Roe v. Wade (60 percent of 50 percent).

In fact, though, the probability is slightly higher than that, because it is possible that more than one of the five justices who currently support Roe will leave the Court in the next four years and that Romney will therefore get two or more bites at the apple. Given that possibility, the odds that Romney will succeed in appointing a justice who will vote to overrule Roe increase to at least 40 percent.

Thus, for those men and women who care about the continuing authority of Roe v. Wade and the constitutional right of women to make decisions for themselves about whether to bear or beget a child, the stakes in this election are very high indeed.