Donald J. Trump has a big decision to make.

In 10 days, the former president will be free to sell his shares in Trump Media & Technology Group — the publicly traded parent company of Truth Social, his social network and main online megaphone. A provision that barred him from selling any of his 115 million shares will expire on Sept. 19.

His stake is worth $2 billion, an enticing bounty given that Mr. Trump invested only a few million dollars into Trump Media, which was formed just weeks after he left the White House in early 2021. But his shares are worth a lot less than they were in March, when Trump Media made its Wall Street debut.

A sale by Mr. Trump would have big implications, both financial and political. It almost certainly would tank the price of Trump Media’s volatile stock, decreasing the value of whatever remains of Mr. Trump’s stake. An ensuing slump in the share price might also leave the company’s more than 600,000 shareholders — many of them supporters of the former president and users of the platform — feeling sabotaged and alienated.

“He has no reason to sell, because he doesn’t need the money,” said Greg Bowden, a 66-year-old self-described day trader and supporter of Mr. Trump who said he owns shares of Trump Media. “I don’t think he’s that stupid to hurt his loyal base of supporters.”

Many investors in Trump Media are already deeply in the red, thanks to a sharp drop in the share price over the past few months. But the presence of a large seller like Mr. Trump could swamp buyers in such a thinly traded stock.

“It’s a supply-and-demand story: If you flood the market with shares, you are just not going to find enough buyers,” said Mike Stegemoller, a finance professor at Baylor University. “You don’t want to shock the market. I don’t think he is dumb in that regard. His self-interest may work to the advantage of the shareholders.”