Which amendment allows citizens 18 years or older to vote?

The 26th Amendment to the United States Constitution is the correct answer as it specifically lowers the voting age to 18 years. Ratified in 1971, this amendment was a response to arguments that those who were old enough to be drafted for military service in the Vietnam War should also have the right to vote. This amendment guarantees that citizens who are 18 years or older cannot be denied the right to vote based on age, ensuring their inclusion in the democratic process.

Understanding this amendment is crucial as it highlights the principle of equal participation in elections. It represents a significant shift in electoral rights, promoting youth engagement in governance and societal issues.