Jonathan Adler is right to suggest that George Will too readily concludes that presidential candidates' positions on abortion should be largely irrelevant to voters. Will claims that a Supreme Court decision overruling Roe v. Wade would restore "moral federalism," a system under which each state could adopt its own preferred policy on abortion. Thus, prochoice voters living in states with prochoice majorities have nothing to worry about (at least so far as their own states are concerned).
I wish that were true. But under the Supreme Court's recent federalism jurisprudence it simply isn't. The Supreme Court's 2005 decision in Gonzales v. Raich held that Congress can regulate any activity with even the slightest, extremely tenuous connection to "commerce." For the detailed explanation why, see my article on Raich. I also explained how Raich gives Congress the power to regulate abortion in this November 2006 post.
In my view, Raich is a severely flawed interpretation of Congress' Article I power to regulate "commerce among . . . the several states." Nonetheless, six Supreme Court justices signed on to it, and all six are still on the Court. Thus, if Roe v. Wade were overruled, current Supreme Court federalism doctrine gives Congress ample power to regulate or ban abortion in pretty much any way it sees fit. Sadly, Will's "moral federalism" has been rejected by the Court and is unlikely to be embraced by Congress of its own accord. Witness their 2003 law banning partial birth abortions, which the Supreme Court recently upheld in Gonzales v. Carhart.
So long as Congress is controlled by the Democrats, it is unlikely that any more federal laws restricting abortion will be enacted. However, the Democratic majority in Congress is narrow and it is not impossible that they will lose it sometime in the next few years. Thus, presidential candidates' positions on abortion are potentially much more important then Will suggests.