When President Obama announced his major second term executive actions on immigration, it was almost immediately clear that it would lead to a Supreme Court showdown. But now that the case is finally at the high court, the conservative forces pushing it will be without a major ally, with Justice Scalia's unexpected death in February. All eyes at Monday's oral arguments will be on Chief Justice John Roberts to gauge how he will navigate his court through an already hyper-political case that the vacant seat further complicates.