Explainer: Why are 500 signatures required to run for president of France?

As France's presidential election approaches, some aspiring candidates say they are still striving to collect the 500 signatures from elected officials required to join the ballot for the first round on April 10. Many an Élysée Palace dream has been dashed when hopefuls have fallen short of that magic number. What is the 500 signatures rule and how does it work? FRANCE 24 explains.