Donald Trump has his own social network called Truth Social.REUTERS/Kevin LamarqueThe value of Donald Trump's Truth Social stake has tanked by about $4 billion since May.The ex-president may face further declines when stock-selling restrictions ease later this month.Trump's social media platform has been hit by Kamala Harris' momentum and his own use of rival X.Donald Trump has seen about $4 billion wiped off the value of his Truth Social stake since May — and could suffer further losses once selling restrictions on the stock are lifted later this month.The former president owns about 115 million shares of Trump Media & Technology Group, Truth Social's parent company.