This not just another tweeter, this the senior Senator from Hawaii

It happened, I got to vote before I was 21. And that happened with the supposed "silent majority" being scared to death of what we might do:

The Twenty-sixth Amendment (Amendment XXVI) to the United States Constitution prohibits the states and the federal government from using age as a reason for denying the right to vote to citizens of the United States who are at least eighteen years old. The drive to lower the voting age from 21 to 18 grew across the country during the 1960s, driven in large part by (1) the military draft that resulted in young men between the ages of 18 and 21 being conscripted into the armed forces, primarily the U.S. Army, to support military combat operations in Vietnam,[1] and (2) the broader student activism movement protesting the Vietnam War. The impetus for drafting an amendment to lower the voting age arose following the Supreme Court's decision in Oregon v. Mitchell, 400 U.S. 112 (1970), which held that Congress may establish a voting age for federal elections, but not for local or state elections.

On March 23, 1971, a proposal to lower the voting age to 18 years was adopted by both houses of Congress and sent to the states for ratification. The amendment became part of the Constitution on July 1, 1971, three months and eight days after the amendment was submitted to the states for ratification, making this amendment the quickest to be ratified