During the jim crow era, southern states imposed poll taxes and literacy tests in order to
prevent african americans from exercising their right to vote.
support the passage of the fifteenth amendment.
encourage citizens to vote in local elections.
discourage african americans from attending school.

Prevent African Americans from exercising their right to vote.

Explanation:

The 15th Amendment to the U.S. Constitution (1870) granted the right to vote to all Americans regardless of their race, for the first time, which included African American, who had been harshly discriminated and mistreated for decades. This was a big step to put a halt on discrimination and gain equality of rights. However, in reality, many white Americans, especially Southerners, fiercely opposed to fully include black people as equal in society. Consequently, they began to enact a series of acts that prevented them from exercise their rights.

Some of the many legislation that Southern states passed during this "Jim Crow era" to prevent African Americans from exercising their right to vote was to impose poll taxes, which sometimes black people could not pay, and to force them to take literacy tests as a requirement to vote, which, again, they often failed.

i would say that the politicial parties from state to state varies.