Sentence:  But it would greatly strengthen any Mayor 's executive powers , remove the excuse in large degree that he <WSD>is</WSD> a captive of inaction in the Board of Estimate , increase his budget-making authority both as to expense and capital budgets , and vest in him the right to reorganize city departments in the interest of efficiency and economy . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)