Sentence:  Mr. Kennedy <WSD>was</WSD> less troubled by that possibility than by the belief that a Geneva breakdown , or even continued stalemate , would mean an unchecked spread of nuclear weapons to other countries as well as a fatal blow to any hope for disarmament . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)