Tesla’s stock gets punished as Musk says he’ll start third political party. ‘This is not the news we want to see.’ T esla investors faced a rough start to the week, with shares dropping after Chief Executive Elon Musk’s plan for a new U.S. political party drew the ire of President Donald Trump — and one downgrade.

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.