Tesla shares fell nearly 8% on Monday after CEO Elon Musk's plans to launch a new U.S. political party reignited concerns about his commitment to the company's future as it struggles with declining sales.

Tesla shares sank Monday after CEO Elon Musk announced he would form a new political party in an escalation of his feud with President Donald Trump.

Tesla investors hoping that CEO Elon Musk would stay out of politics after leaving his position in the Trump administration are going to be sorely disappointed—again. Disappointment is rarely good for stock prices.