(CNN) The United States is a democracy, which means everyone gets to vote in US elections, right? Wrong.

Who gets to participate and how easy it is for those voters to cast their ballots has been an ongoing fight since the Constitution was written.

What exactly does the Constitution say about who gets to vote? Not much. "The people" choose congressmen. States are in charge of elections and Congress can overrule them. And electors, not voters, choose the President.

That system did not last long.

There are not one or two but SEVEN constitutional amendments that deal directly with who gets to vote and how. And a lot of laws have been passed since then, too.