Line Item Veto --- NPR's Nina Totenberg previews today's arguments in a Supreme Court case challenging the Constitutionality of the line item veto. The law gives a President the authority to veto specific items in a spending bill passed by Congress without vetoing the entire bill. It was passed last year by the Republican Congress and signed by President Clinton. Leading the challenge is Senator Robert Byrd of West Virginia, who fought unsuccessfully to prevent the law's passage. His lawyers will argue that it tilts the balance of power from the legislative to the executive branch, something that can be done only by Constitutional amendment, not by statute.