Final answer:
Robert F. Kennedy emerged as the preferred candidate among liberals in the 1968 Democratic Party for his strong stance on civil rights, his reconciliation with labor unions, and the broad coalition of support he garnered, which included minority groups, women's rights activists, and nonunion workers.
Step-by-step explanation:
In the 1968 presidential campaign, Robert F. Kennedy became the candidate of choice for many liberals associated with the Democratic Party for several reasons. His advocacy for civil rights played a significant role, appealing to African Americans, minorities, women's rights activists, and younger voters, especially given the fractured state of the Democratic Party at the time. An arguably more humanistic appeal was demonstrated by Kennedy’s swift action following the assassination of Martin Luther King Jr., which solidified his respect among African American communities.
Kennedy's positions were in alignment with key Democratic groups, including labor unions, which he had managed to reconcile despite previous aggressive tactics. Furthermore, his support for Cesar Chavez and the rights of migrant workers expanded his appeal among various voter groups disillusioned with the other Democratic candidates and the Republican Party. Kennedy's ability to attract a broad coalition of supporters made him a strong potential candidate to unify the party.
Unfortunately, Kennedy's assassination on June 6, 1968, during his campaign, ended the hope of many for a united and progressive push forward on crucial issues such as civil rights and social justice during a deeply tumultuous era in American politics. Ultimately, his campaign promised a progressive future that resonated with a wide array of Democratic voters, marking him as the liberal beacon in a time of national discord.