The Musk effect still underpins Tesla’s market cap. The shareholders who have pumped up its stock price are fixated on the technology future that he has conjured up, not the electric car business that is the company’s bread and butter today.

The world's richest man's latest political activities prompted a brutal sell-off of Tesla stock as investors question his focus on the company.

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.