The number of American military personnel in Vietnam increased dramatically, from 16,000 soldiers in 1963 to over 500,000 in 1968. Growing anger with the war stimulated a large antiwar movement based especially on university campuses in the U.S. and abroad. Johnson faced further troubles when summer riots broke out in most major cities after 1965. In the 1960 presidential election, the Kennedy-Johnson ticket narrowly defeated the Republican ticket led by Vice President Richard Nixon. Johnson played a frustrating role as a powerless vice president, rarely consulted except specific issues such as the space program.Kennedy was assassinated on November 22, 1963, while riding in a presidential motorcade through Dallas. He took office determined to secure the passage of Kennedy's unfinished domestic agenda, which, for the most part, had remained bottled-up in various congressional committees.