One of the most tumultuous primary election seasons ever began as the Tet Offensive was launched in January 1968 . President Johnson withdrew as a candidate in March , after doing unexpectedly poorly in the New Hampshire primary . In June , Senator Robert F. Kennedy , a Democratic candidate , was assassinated just moments after his victory in the California primary . On the Republican side , Nixon 's main opposition was Michigan Governor George Romney , though New York Governor Nelson Rockefeller and California Governor Ronald Reagan each hoped to be nominated in a brokered convention . Nixon secured the nomination on the first ballot . He selected Maryland Governor Spiro Agnew as his running mate , a choice which Nixon believed would unite the party , appealing to both Northern moderates and Southerners disaffected with the Democrats
was assassinated
Assassination of Robert F. Kennedy
Richard Nixon