BARCELONA, Spain (AP) — For the first time in 20 years, Florentino Pérez’s Real Madrid reign will be challenged at the ballot box.The world’s most valuable and most successful soccer club will hold elections on Sunday.Pérez, the 79-year-old executive who for the past two-and-a-half-decades has made Madrid the global powerhouse to beat, will face an upstart rival half his age who is making big promises to convince the club’s 98,000 members to consider a change.Enrique Riquelme, 37, was still a boy when Pérez first took over. He remained unknown to most Madrid fans until he stepped forward as a rival candidate after the incumbent called early elections last month in a press conference dominated by Pérez’s claims the Spanish media is trying to “kill” his presidency.“Why do they want to kill me?” an agitated Pérez told reporters on May 12. “Why? Because there are some kids out there saying they want to run? Well, let them. I would love them to.”Riquelme, a renewable energy executive, has surprisingly been able to mount a credible threat. That’s thanks to the backing of former Madrid players like Raúl González and promising huge, and arguably far-fetched, signings like that of Manchester City star Erling Haaland.