Read this passage from 'We Shall Overcome." We cannot, we must not, refuse to protect the right of every American to vote in every election that he may
desire to participate in. And we ought not, and we cannot, and we must not wait another eight months before
we get a bill. We have already waited a hundred years and more, and the time for waiting is gone.
How does the parallel structure in the passage contribute to the persuasiveness of the speech?