Given a sentence and two mentions from the text (arguments), indicate a phrase (a verb or noun phrase) that describes the relationship between the provided arguments.
Q: Sentence: 'The opening statements of the 18 senators who will first vote on John Roberts ' nomination for Chief Justice of the United States set the stage for the confirmation battle .', Argument/Subject 1: 'john robert', Argument/Subject 2: 'unite state'
A: 
be chief justice of