march in protest
take part in a demonstration "Thousands demonstrated against globalization during the meeting of the most powerful economic nations in Seattle"
provide evidence for
stand as proof of
show by one's behavior, attitude, or external attributes "His high fever attested to his illness" "The buildings in Rome manifest a high level of architectural sophistication" "This decision demonstrates his sense of fairness"
establish the validity of something, as by an example, explanation or experiment "The experiment demonstrated the instability of the compound" "The mathematician showed the validity of the conjecture"
give an exhibition of to an interested audience "She shows her dogs frequently" "We will demo the new software in Washington"