How did the united states try to influence vietnam’s national elections in 1956?
it hired soldiers to overthrow ngo dinh diem.
it hired soldiers to overthrow ho chi minh.
it backed ngo dinh diem as president in south vietnam.
it backed ho chi minh as president in south vietnam.

The right answer is It backed Ngo Dinh Diem as president in South Vietnam. Let's understand how:

The Geneva Accords of 1954 divided Vietnam in half at the 17th parallel, with the communist block in the north and the south. This accord also requested for elections, within 2 years, in all Vietnam in order to reunify the country. Fearing the expansion of Communism in the world, the US was opposed to the elections. In 1956, the South Vietnamese president, supported by the US, successfully blocked the unifying elections.

a reason that was key to coolidge's victory in the 1924 presidental election was that; democratic party supporters were split in the north and south.