First, we must define the original definition for who is allowed to vote to be able to understand what exactly is expanded upon. At the conceiving of this nation, the white male, land-owning, 21-year old and older were allowed to vote. Meaning, females, people of other skin-color (or even mixed), and non-land owning entities were not allowed to vote. The first change to the right to vote occurred in 1860, and African Americans gained the right to vote 10 years later when the amendment was passed. Following this, Women were allowed to vote in 1920, which saw the rise of support for women (and Native Americans), as they were essentially citizens, and to deny citizens their basic rights was against the natural rights espoused to all when they were born. Of course, with the right to vote comes the responsibility of such a vote. A person is expected to vote for such people in which they believe are aligned to their personal beliefs, as well as what is "better" for the nation. On top of that there would be responsibilities espoused to citizens, such as jury service, etc.
However, while the rights of who and what for voting has expanded, restrictions has also occurred, such as non-citizens (obviously), as well as criminals and felons.
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