The nomination of Harriet Miers to the Supreme Court was not derailed in the United States Senate, which has a constitutional obligation to advise and consent on the president’s picks. It was killed by members of President Bush’s own party, unconvinced by her conservative bona fides and, especially, her position on abortion.

With his new nominee, the president has picked a man of unquestionable conservative credentials and a public record on abortion. Unlike Miers and Chief Justice John Roberts, who were often called stealth nominees because they lacked lengthy paper trails defining their views on controversial issues, Judge Samuel Alito has a long history of opinions to bolster his supporters and enliven his critics.

Whether Alito would vote to overturn Roe v. Wade, the Supreme Court decision that guarantees a woman’s right to have an abortion, is hard to predict, but he has supported laws that placed strict limitations on abortion rights.

On other issues, he has written opinions supporting laws that would make it harder for workers to win discrimination claims and questioned the authority of Congress to enact the Family and Medical Leave Act.

While Alito’s nomination may act as a salve to heal the frayed relations between President Bush and the right wing of the Republican Party and provoke an all-out confirmation battle with Democrats, it also puts Maine’s two moderate, pro-choice Republican senators in a difficult position.

Sens. Olympia Snowe and Susan Collins will be forced to decide whether their support for the president goes beyond their commitment to abortion rights or other social issues and whether a possible Democratic filibuster of this nominee would trigger a potential rule change that had been narrowly avoided during earlier judicial confirmation fights.

Special-interest groups on both the right and left have been spoiling for a Supreme Court confirmation fight, convinced that the majority of Americans agree with them. With Alito, it looks like they’ll get what they want, while it’s folks in the middle who are really going to feel the political squeeze.