Mr. Musk’s involvement in politics and his financial support for the president’s campaign were once seen by investors as a benefit to Tesla, fueling a steep rise in company shares after the election last year. That association has now turned into a liability. Tesla shares are down 40 percent from their peak in December.

Tesla stock price fell Monday after Musk said he's formed the America Party, the latest development in the billionaire's feud with President Trump.

Longtime supporters of Tesla and Elon Musk called on its board to pull the CEO back to the troubled EV maker after he said he is starting a new America Party.

Elon Musk says he has formed a new political party called the America Party. But it remains unclear what formal steps, if any, he has taken to establish it.