WASHINGTON — When the Supreme Court heard arguments in a major abortion case from Mississippi in December, it was clear to observers that there was substantial support among the court’s conservative majority for overruling two landmark decisions that established and reaffirmed a woman’s right to an abortion.So when a draft of the opinion in the case written by Justice Samuel Alito was leaked late Monday the potential outcome — the overruling of Roe v. Wade and Planned Parenthood v. Casey — was …