Threat-making has suddenly taken over politics, thanks to the Supreme Court vacancy created by the retirement of Justice Sandra Day O'Connor.

"For President Bush, social conservatives, and the senators they helped elect, the moment of truth has arrived," Richard Land of the Southern Baptist Convention told The New York Times. That's a threat from the Right.

Here's one from the Left: "If the president abuses his power and nominates someone who threatens to roll back the rights and freedoms of the American people, then the American people will insist that we oppose that nominee, and we intend to do so," Sen. Edward Kennedy, D-Mass., said on the Senate floor.

The most endangered rights involve abortion. They might get "rolled back" to where they stood before 1973, when the Supreme Court handed down its Roe v. Wade decision recognizing a constitutional right to abortion. For conservatives like Land, "the moment of truth" means forcing Republicans to deliver what the party has promised in its platforms since 1980—a Supreme Court that will overturn Roe.

O'Connor voted in 1992 to reaffirm Roe. Conservatives demand that Bush nominate someone who they can be certain would vote to reverse it. That raises the issue of a "litmus test": Should the White House or Senate require a nominee to answer the question, "How would you vote on Roe v. Wade?"

Conservatives rally to the cry, "No more David Souters." Souter, nominated to the high court by President George H.W. Bush in 1990, refused to submit to the litmus test. Conservatives were outraged when, after winning confirmation, he turned out to support abortion rights. "We do not want another wolf in sheep's clothing," declares Tony Perkins, president of the Family Research Council.

Many liberals denounce the idea of a litmus test. "I don't set up a litmus test for any particular nominees," Kennedy said last week. "I have voted for judges who have been 'pro-life.' " But Nancy Keenan, president of NARAL Pro-Choice America, has warned the president not to nominate a "stealth candidate" whose position on Roe is unknown.

What kind of threat can liberals make with Democrats a minority in the Senate? They can demand that Democratic senators assert their right to filibuster the nomination, on the grounds that a threat to roll back abortion rights is an "extraordinary circumstance." After all, when a Gallup Poll for CNN/USA Today asked voters whether they would prefer a new Supreme Court justice who would vote to uphold Roe or one who would overturn it, the answer, by more than 2-to-1 (65 to 29 percent), was one who would uphold Roe.

The pressure will be on the "Gang of 14" senators who in May struck a compromise over the use of the filibuster. The seven Republicans promised not to vote for the "nuclear option" that would ban filibustering judicial nominees. In return, the seven Democrats promised not to use the filibuster to block votes on judicial nominees, except in "extraordinary circumstances."

If the president nominates a justice who pledges to overturn Roe, look for liberals to demand a filibuster and conservatives to call for pulling the "nuclear" trigger. "The nuclear option is definitely on the table," Sen. John Warner, R-Va., one of the Gang of 14, told The New York Times. Warner added ominously that if Senate Republicans change the rules to confirm a nominee, "that justice would be tattooed with the nuclear option for the rest of his or her life on that Court."

The threats will be felt most keenly by senators up for re-election next year, including six members of the Gang of 14: Republicans Lincoln Chafee of Rhode Island, Mike DeWine of Ohio, and Olympia Snowe of Maine, and Democrats Robert Byrd of West Virginia, Joe Lieberman of Connecticut, and Ben Nelson of Nebraska, plus two senators facing potentially close races: Republican Rick Santorum of Pennsylvania, a blue state, and Democrat Bill Nelson of Florida, a red state.

In theory, no one can threaten President George W. Bush. He can't run again. But his popularity has been dropping. Further erosion could doom his plans for Iraq and for overhauling Social Security and the tax code.

Conservatives intend to hold him to a declaration he made during his first presidential campaign. As Rich Lowry, editor of the National Review, put it, "One of the reasons that conservatives were enthusiastic about him, going back to 2000, was that he said he was going to appoint strict constructionist judges in the mode of [Antonin] Scalia and [Clarence] Thomas. To back off that would create a firestorm on the right."

Democrats intend, meanwhile, to try to hold Bush to his 2000 promise to be "a uniter, not a divider." Senate Minority Leader Harry Reid, D-Nev., said, "President Bush should use this opportunity to bring the country together, not to tear us apart." Some Republicans, like Warner, agree. In Warner's view, "This nomination of the first Supreme Court justice by this distinguished president gives him an opportunity to be a uniter, not a divider."

For the vast majority of voters in the middle, it's not clear whether abortion is a litmus-test issue. Most voters accept the view of abortion rights that the Supreme Court reaffirmed in its 1992 decision—abortion is a constitutionally protected right that can be limited and regulated. The co-author of that decision? Sandra Day O'Connor.