Wall Street's main indexes opened lower on Monday as tariff tensions kept investors on edge, while Tesla shares slid after CEO Elon Musk announced his plans to launch a political party.

Wall Street faces uncertainty as Tesla shares drop after Elon Musk announces a new political party. Discover the impact.

Mr. Musk’s involvement in politics and his financial support for the president’s campaign was 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.