Teslasselloff on Wall Street intensified on Monday, with shares of the electric vehicle maker plunging 15%, their worst day on the market since September 2020.On Friday, Teslawrapped upa seventh straight week of losses, its longest losing streak since debuting on the Nasdaq in 2010. The stock has fallen every week since CEOElon Muskwent to Washington, D.C., to take on a major role in the second Trump White House.Since peaking at $479.86 on Dec. 17, Tesla shares have lost over 50% of their value, wiping out over $800 billion in market cap. Monday marked the stocks seventh worst day on record.Tesla led abroader slumpin U.S. equities, with the Nasdaq tumbling almost 4%, its steepest decline since 2022.The downdraft in Teslas stock on Monday was tied to uncertainty surroundingPresident Donald Trumpsplans on tariffs. Canada and Mexico are key markets for automotive suppliers, and increased tariffs, with the potential for a trade war, will likely impact production and lead to higher prices.Tesla is also dealing with brand erosion due to Musks incendiary political rhetoric and his extensive work with the Trump administration, where hes leading up the so-called Department of Government Efficiency. Musk, the worlds wealthiest person, has become the public face of the administrations effort to dramatically shrink the federal governments workforce, spending and capacity.Meanwhile, Musk has used his social network X to level accusations against judges whose decisions he didnt like and promoted false Kremlin talking points about Ukraine President Volodymyr Zelenskyy.Activists and former Musk fans have protested at Tesla facilities throughout the U.S., and Tesla vehicles and facilities have been the apparent targets of vandalism and arson attempts. Repeated arson attempts and instances of vandalism occurred at a Tesla store and service center in Loveland, Colorado, most recently on March 7, police told CNBC.Ben Kallo, an analyst at Baird, told CNBCs Squawk on the Street on Monday that recent reports of vandalism could hurt demand.When peoples cars are in jeopardy of being keyed or set on fire out there, even people who support Musk or are indifferent Musk might think twice about buying a Tesla, Kallo said.Analysts at Bank of Americas wrote in a report on Monday that Tesla new vehicle sales plummeted by about 50% in Europe in January from a year earlier, partly owing to growing distaste for the brand. The firm also noted that some prospective customers are waiting for the new version of the Model Y.Teslas Model Y, which is a small SUV, remained the best-selling battery electric vehicle globally in January. It was followed by Chinas Geely Geome, which surpassed the Tesla Model 3 sedan for the month.Global sales of electric vehicles, including fully electric and plug-in hybrid models, increased 21% in January from a year ago, even as Teslas sales declined. The growth was driven by demand in Europe, according to Bank of America. CNBCs Jesse Pound contributed to this report.More from CNBC: