Tesla resale values are cratering as owners sell up amid an escalating backlash over Elon Musk's involvement with DOGE.The average price of a used Tesla fell more than 10% in March compared to the same period last year, according to data from used car listing website iSeeCars.This was the largest drop of any car brand in iSeeCars' data.Prices for pre-owned Model S and Model Y vehicles collapsed 17.2% and 13.1% year-over-year, with the average price of a Model 3 now just over $26,000.That is despite the average price of used cars overall rising slightly in March for the first time in two and a half years, per iSeeCars' data.It comes as a growing number of Tesla owners sell their vehicles as global protests against Tesla CEO Musk gather momentum.Used car site Autotrader saw a record number of Tesla listings in March, according to its parent organization, Cox Automotive, while data from Edmunds reported by Reuters suggested that Tesla trade-ins hit a record high last month.Musk's work cutting federal spending under the Trump administration has turned Tesla vehicles and showrooms into a target for protests and vandalism, and alienated some of the company's traditionally liberal customer base.Several former Tesla owners previously told Business Insider they had sold their cars in response to Musk gutting the federal workforce, with some saying the spate of vandalism against Tesla vehicles played a part in pushing them to sell.Used Tesla values have been dropping steadily over the past few years as the automaker has slashed the prices of its new vehicles.While that's good news for buyers who want to pick up a pre-owned EV at a discount, it's less positive for long-time Tesla owners looking to sell their cars.Tesla investor Ross Gerber told BI last year he was struggling to flip his old Tesla because he couldn't get a fair price for it, and owners who decide to sell today may have to take a serious haircut.The collapse in used values comes as Tesla's new car sales also struggle.The company announced underwhelming first-quarter deliveries earlier this month, with sales cratering in Europe and China as Tesla faces a "brand crisis tornado" over Musk's political interventions and surging competition from EV rivals.