Yes, people can register to be members of any party or non-partisan. The advantage of registering with a certain party is that you can then vote in the primary elections earlier in the year to help decide the candidates for each party.
Other reasons people do not register to vote is that a great many people prefer to "stay off the grid" as it were. Registering to vote is a pretty blatant admission of your own existence. If a person wishes to remain more anonymous (as many, mostly paranoid or criminal persons do), registering to vote is probably not a great idea.
The final date for registration has already passed. You would never be able to register at the polls. In addition to many boothes set up in every mall, at various businesses, etc., a person can also register at the Election Commission office. Also, groups can go door-to-door with voter registration forms.
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Goodbye Ruth & Betty, my beautiful grandmothers.
Betty Kuzara 1921 - April 5, 2008
Ruth Kellison 1925 - Dec 27, 2007