in the election of 1868, republican party candidate, ulysses s. grant, won the presidency by only a narrow majority of the popular vote. he received support from free black voters in the south. without that support, he probably would have lost the election. at the time blacks could not vote in the northern states. the republican party needed help to stay in power and thought that black votes would help. at the time republicans controlled both the senate and house. the proposed amendment was passed by congress in 1869 and sent to the states for ratification. it was quickly ratified by three-quarters of the states in early 1870. part of the reason why is that republicans also controlled the state governments in the south. southern democrats were not able to block the measure.