The film chronicles the life of Lyndon B. Johnson, focusing on his unexpected ascent to the presidency following the assassination of John F. Kennedy. The narrative is primarily set against the backdrop of the 1960s, a tumultuous period marked by significant political and social upheaval in the United States. It begins with Johnson, a seasoned politician from Texas, who finds himself as Vice President after a contentious campaign alongside Kennedy. Johnson's ambition and political savvy are evident, yet he struggles for influence in an administration dominated by Kennedy and his close-knit circle.

As the story unfolds, Johnson wrestles with his own ambitions while navigating complex relationships with other key political figures. His transformation from a marginalized Vice President to a national leader comes unexpectedly when he is thrust into the presidency amid national tragedy and crisis. The film delves into Johnson's efforts to unify the nation, seeking to implement his vision for civil rights and social reforms, while facing immense opposition. The narrative captures the human side of Johnson, revealing his vulnerabilities, tenacity, and eventually, his decisive moments as he grapples with guiding the country through a challenging era.