    Sentence 1: Bush 's aides describe Omaha  as the most crucial stop , since Sen.  Ben Nelson ( D-Neb . ) has become their  top Lobbying target on the tax cut  package .    Sentence 2: Bush 's aides describe Omaha  as the most crucial stop , since Senator  Ben Nelson , Democrat of Nebraska , has  become their top Lobbying target on the  tax-cut package