Summary- how realignments progress-

 has its origins in the rise of a new political issue, that new issue must cut across the existing line of party cleavage. The parties cant deal with the issue, it just cant be any old issue it has to be potent to make side take opposing position. The electorate has to be able to understand them. Importantly they have to take opposing issues on the position then people cant sort themselves into the appropriate party.
 Third big thing- generally when such an issue arises- the first impulse of the people running the parties is to ignore it. They want to change the subject( environment) those that are invested in the issue are trying to make everyone pay attention.