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.

Elon Musk said he would form a new political party called the "America Party." Tesla shares fell around 7% in premarket trading on Monday after Musk's announcement. Tesla shareholders have wanted Musk to stay away from politics,