So what else is at stake in Ayotte? In the 1992 case of Planned Parenthood v. Casey, Sandra Day O'Connor created something called "the undue burden standard." Under this standard, if an abortion regulation is likely to be unconstitutional as applied to a significant number of women, then the law itself is unconstitutional.

So, for example, when Congress recently passed a partial-birth abortion ban, pro-choice groups suing to overturn such laws don't need to prove that the law would be unconstitutional as applied to every single woman under every imaginable set of circumstances. The fact that the ban made no provision to protect women's health-meaning that it would be unconstitutional if applied to women who need "partial birth" abortions for health reasons-was enough to cause the law to be blocked entirely.

In Ayotte, Connecticut is asking the Supreme Court to replace this aspect of O'Connor's undue burden standard with something called the "Salerno standard." Under the Salerno standard, if an abortion ban would be constitutional as applied to any women at all, in any set of circumstances, then the law can not be completely overturned. Brad of Think Progress sums of the consequences of that:

It seems unlikely—indeed, virtually impossible—that the Court would use Ayotte to overrule Roe. But if the Court reaches the second question and holds that Salerno governs facial challenges to abortion regulations, it would dramatically undercut the right to choose. As Jack Balkin has explained, such a rule would mean that "almost no new abortion regulations can be halted before they take effect; instead, plaintiffs must make a series of individual challenges to specific aspects of the law that affect them personally. These as-applied challenges will take months or even years before they are finally resolved, and the remainder of the new abortion regulations will be enforceable in the interim." That is, very restrictive regulations could remain in place for years so long as they were constitutional as applied to some women, forcing many of those who seek abortions to risk criminal prosecution.

In short, many of the rights guaranteed women by Roe and Casey could be eviscerated by Ayotte-but in a quiet, technical fashion that would protect the Republican party from voter backlash.

It's by no means inevitable that the Salerno standard will be applied to abortion cases. It seems unlikely that the anti-Choice members of the Court could make this radical change without getting Justice Kennedy on their side; and Kennedy, although not a reliable pro-choice vote, might not be willing to go that far. Nonetheless, for pro-choice activists following happenings at the Supreme Court, the Salerno standard is the gravest immediate threat to reproductive rights.

Pro-choicers should follow the Ayotte case closely.

More blogging about Ayotte:

SCOTUSblog, SCOTUSblog again, All Deliberate Speed, Think Progress, Balkinization, and ACSBlog.