Final answer:
Ngo Dinh Diem refused to conduct the nationwide elections mandated by the Geneva Accords in 1956, instead holding a fraudulent referendum that installed him as president of South Vietnam. This action and his autocratic regime led to increased unrest and resistance, contributing to the intensification of conflict in Vietnam.
Step-by-step explanation:
During the Vietnamese election in 1956, Ngo Dinh Diem refused to participate in the nationwide elections that were mandated by the Geneva Accords for the reunification of Vietnam. Instead, Diem, supported by the United States for his anti-communist stance, held a fraudulent referendum in South Vietnam in 1955, where he was declared president with an implausibly high majority. This action canceled the planned elections and intensified unrest in South Vietnam, leading to brutal repression of dissidents and the marginalization of Buddhists.
Diem's autocratic rule and oppressive regime, coupled with corruption, ultimately made him extremely unpopular, contributing to the increasing turmoil and aiding the growth of the National Liberation Front, which sought to support North Vietnamese efforts to reunify the country under communist leadership.