Why do you think civil rights leaders such as john lewis thought it was essential for african americans to gain the right to vote? why do you think they thought it would their cause?

Voting rights were and are considered a fundamental right of any citizen. If African Americans were to be recognized as equal citizens and participants in the nation, the right to vote was essential.  All sorts of barriers and rules were constructed intended to block blacks from registering as voters, and events such as the march from Selma to Montgomery in 1965 were aimed at ending that system of discrimination. 

John Lewis and others in the civil rights movement sought to help their cause by drawing national attention to the matter and the attention of the highest leaders in government.  After the violence they first met when trying to march from Selma, John Lewis said that he didn't understand how President Johnson could send troops to Vietnam but not send troops to Alabama to protect people whose only desire was to register to vote.  And then President Johnson did send troops to protect the marchers, and within a week made a major speech to Congress and introduced the Voting Rights Act.  So they did, in fact, help their cause by their actions in regard to voter registration rights.

No , abraham lincoln is elected 16th president of the united states over a deeply divided democratic party, becoming the first republican to win the presidency . lincoln receive 40 % of the popular vote handily defeated three other candidates