In just over three weeks Americans go to the polls. But who actually gets to vote is set to be one of the big controversies of the election, with states being given greater freedom to set their own laws.

The seeds for what could become a messy patchwork across the country were sown by the Supreme Court in June 2013 when it effectively gutted the 1965 Voting Rights Act.

The ruling paved the way for a wave of litigation, which could see the courts of law proving as important as the court of public opinion.

What is the Voting Rights Act?

Regarded by many as the crowning achievement of Lyndon Johnson’s administration, the Act was signed into law in August 1965.

Introduced in the teeth of opposition from southern Democrats, the law swept away the 19th century Jim Crow laws which were designed to prevent emancipated slaves registering to vote.

The worst abuses included a discriminatory literacy test which, in some cases, saw black voters being asked to recite the entire Constitution or Declaration of Independence.

It forced nine states to get federal approval before being allowed to change their voting laws.