New York CNN  —  Former President Donald Trump’s social media fortune is shrinking. The value of Trump’s stake in the corporate owner of Truth Social has dropped by $900 million since Vice President Kamala Harris entered the race for the White House on July 21. Trump Media & Technology Group’s share price has tumbled by about 23% since then, including another sharp drop on Thursday amid a broader market selloff. The value of Trump’s dominant stake in the conservative social media company stood at just over $4 billion as of July 19, the final trading day before President Joe Biden exited the race and endorsed Harris. It has since dropped to about $3.1 billion.