Roe v. Wade was decided in 1973 by a 7-2 vote. By 1992, after Court appointments by Presidents Ronald Reagan and George H.W. Bush, the Court had made significant progress, voting in Planned Parenthood v. Casey to uphold Roe by only a 5-4 margin. And even that ruling -- while extremely flawed and disappointing -- revised Roe in ways that made more state-level pro-life laws (e.g., informed consent, waiting periods) possible, leading to modest but substantial reductions in the number of abortions through the 1990s and 2000s (abortions in the United States have dropped 25 percent since 1990). Those lifesaving laws could not have been enacted without the Supreme Court justices chosen by Reagan and Bush.
The election of Bill Clinton set us back. After his two pro-Roe nominees, the Court held a 6-3 pro-Roe majority and even voted to strike down a state ban on the barbaric partial-birth abortion procedure. Then George W. Bush took office. Bush replaced one anti-Roe justice (Rehnquist) with (probably) another (Roberts) and one pro-Roe justice (O'Connor) with (probably) an anti-Roe justice (Alito). So the balance was again 5-4 in favor of Roe -- just one vote away from having the votes necessary for a reversal. Moreover, the replacement of O'Connor with Alito allowed the Court to uphold (by a 5-4 margin) the federal partial-birth abortion ban in 2007's Gonzales v. Carhart, reversing the earlier decision. It was the first time since Roe that the Court had sustained a ban on a particular abortion procedure, and it set the stage for further incremental challenges to the Court's jurisprudence, such as laws protecting pain-capable unborn children that have been recently enacted across the country.
After Bush left office, over the last four years, two pro-Roe justices stepped down. But the opportunity to overturn Roe was lost because we had elected Barack Obama, who replaced those justices with two more pro-Roe justices.
Here is the historical bottom line: The elections of Ronald Reagan, George H.W. Bush and George W. Bush affected the Supreme Court in ways that have saved many lives from abortion -- and contributed to the future reversal of Roe v. Wade. The elections of Bill Clinton and Barack Obama did the opposite. Reagan and the two Bushes were pro-life and favored judges who are faithful to the Constitution; Clinton and Obama support Roe and unlimited abortion and favor judges inclined to substitute personal (always pro-abortion) policy preferences in place of the law, the same philosophy that gave us Roe in the first place.
Now to the 2012 presidential election. Mitt Romney, unlike Obama, is pro-life, opposes Roe v. Wade, and pledges to choose judges who "adhere to the Constitution and the laws as they are written, not as they want them to be written." The Court is still tipped 5-4 in favor of Roe. A single nomination to the Court by a President Romney could make all the difference; more selections by Obama could cement Roe for another generation.
What would overturning Roe mean? It would mean that the Court is no longer imposing a nationwide policy of abortion on demand. It would mean that states are free to democratically determine their own abortion policies -- there would be a more serious public abortion debate. Some states would retain pro-abortion laws, but many would very significantly limit or even ban elective abortion. Overturning Roe would save the lives of millions of unborn children.
But more than Roe hangs in the balance. A second Obama term could turn the Court against modest pro-life laws that the Court has previously upheld, in decisions like Casey and Gonzales. Obama's two appointees so far would likely vote to strike down partial-birth abortion bans, for example; an additional nomination could put that position in the majority. Obama himself embraces such a radically expansive interpretation of the (fictional) constitutional right to abortion that he thinks the Court should strike down legal protection for born-alive abortion survivors.
Moreover, as Michael Fragoso notes, a president's nominations to other federal courts also affect abortion policy:
At the end of July, [George W. Bush-appointed] Judge Gruender (again) upheld South Dakota's informed-consent law. ... Earlier this year [Reagan-appointed] Judges Jones and Smith thwarted Planned Parenthood's efforts to use the courts to perform an end-run around Texas's popular sonogram law. In 2009, [George H.W. Bush-appointed] Judge Niemeyer upheld Virginia's partial-birth abortion ban en banc.So why does the Supreme Court matter in this presidential election? Because the reversal of Roe v. Wade is at stake. Because pro-life laws are at stake. And because, above all, human lives are at stake.
Given the Supreme Court's 2007 Carhart decision, the presence of conservative judges on the circuits will be crucial to advancing effective incremental pro-life legislation. These incremental changes are proven to be effective and are proliferating at the state level.