Why did Robert Kennedy challenge Johnson for the democratic nomination?

Robert Kennedy challenged President Lyndon B. Johnson for the Democratic nomination in 1968 primarily due to his opposition to the Vietnam War and a desire for a shift in leadership and policy direction. Kennedy believed that Johnson's administration was failing to address critical social issues and civil rights, and he sought to inspire a new vision for America. Additionally, Kennedy's strong connection with grassroots movements and a belief in social justice fueled his campaign, appealing to a generation seeking change. This challenge ultimately reflected the broader discontent within the Democratic Party and the nation during that turbulent period.