"Old enough to fight, old enough to vote." That was the rallying slogan of the 26th Amendment, which lowered the voting age to 18 years old (although the same idea had started somewhere around WWI). The Amendment gained traction while the United States was involved in the Vietnam War conflict. Because so many men between ages 18 to 20 were being drafted to fight, Congress came under enormous pressure to lower the voting age. Many states had already done so, but it took awhile for the federal government to catch up.

And like so many other amendments, this one came in direct response to a Supreme Court ruling: Oregon v. Mitchell (1970), which dealt with what power Congress had to regulate voting.  Congress responded to the opinion by proposing the 26th Amendment. Reports published at the time advanced three main arguments in support of a lowered voting age: (1) that "younger citizens are fully mature enough to vote;" (2) that 18-year-olds "bear all or most of an…