MARCEL Amon-Tanoh, a longtime ally of President Alassane Ouattara and until recently his foreign minister, declared on Wednesday he would run in Ivory Coast's presidential election in October, breaking with the ruling party. The campaign was thrown into uncertainty earlier this month when Ouattara's choice to succeed him after a decade in power, Prime Minister Amadou Gon Coulibaly, died suddenly, leaving the ruling RHDP party scrambling to choose a replacement candidate. The October 31 election is seen as a key test of stability for Ivory Coast, the world's top cocoa producer. Ouattara's first election win in 2010 sparked a civil…