When the Constitution was being framed and the Legislature was being structured, a debate arose among the states. Smaller states wanted equal representation while the larger states said it was not fair to have equal representation with states with smaller population as equality would be trampled on.
The Great Compromise was therefore reached where it was decided that there would be two Houses in the Legislature: the Senate where there would be equal representation and the House of Representatives where there would be representation based on population.
It is important for Americans to vote because once said "One vote changed our senate completely ". In other word a single vote can change everything about what is a law and what is not.
The main reason why President Johnson was unable to stop radical Republicans from putting the reconstruction plan into action is because he simply lacked a congressional majority of backs for his plan.