From Washington to Wall Street, Trump has built an expectation that the federal government will spend serious money on fusion, with the TMTG-TAE entity as a big winner, according to analysts at investment bank Wedbush Securities. TAE will "clearly have major political support from President Trump in our view, and this importantly will create a major nuclear-fusion U.S. energy domestic bet over the coming years," said the Wedbush analysts, led by Dan Ives, in a note to clients.

Rep. Don Beyer, a Virginia Democrat who co-chairs the House Fusion Energy Caucus, noted there are at least 28 fusion companies in the U.S. He said that the key area where he'd have concerns about conflicts of interest involving TAE is if the federal government started providing more money to the fusion industry. He cited one bipartisan study that has called for a $10 billion investment over the next three years.

"I don't want the Department of Energy to be putting its thumb on the scale for any one company," Beyer said, adding that government officials can feel "just the subtle pressure of knowing that the president is interested in this one company."

One former member of the Nuclear Regulatory Commission, appointed during the Carter administration, told MarketWatch that he can't think of an instance in decades with this type of potential for conflicts of interest.