With Saturday’s death of Justice Antonin Scalia, the most important conservative voice on the Supreme Court in decades, the nation may be heading into a constitutional crisis. Senate Republicans are vowing to block President Obama from filling Scalia’s seat. His death will also have an immediate impact on how the now eight-person court will rule in several key cases on the docket this term, including abortion, contraception, unions, voting rights, affirmative action, immigration and the status of Puerto Rico.