WASHINGTON (AP) — In the clearest sign yet of the impact of Justice Antonin Scalia's death, U.S. labor unions scored a major victory Tuesday with a tie vote in a high-profile Supreme Court case they had once seemed all but certain to lose.The 4-4 split, in a case that sharply divided the court's liberal union supporters and their conservative opponents, demonstrated how much is riding on President Barack Obama's effort to replace Scalia with a judge who could tilt the balance on the high court for years to come.