Final answer:
Johnson aligned with traditional Democratic Party leaders who catered to unionized, blue-collar, and White ethnic groups, and after his withdrawal, VP Humphrey continued this legacy.
Step-by-step explanation:
Johnson most closely aligned with the traditional leaders of the Democratic Party who appealed to unionized, blue-collar constituencies, and White ethnics. After President Johnson announced his withdrawal from the presidential race, his vice president, Hubert H. Humphrey, took up the mainstream Democratic Party's torch. This faction supported Johnson's Great Society programs and represented one of the primary forces within the Democratic Party at the time, alongside other groups such as idealistic young activists, a coalition of Catholics, African Americans, other minorities and some young antiwar elements, and the southern Democrats or Dixiecrats.