Why Tesla's rally may have a short fuse Tesla stock seems to be flying on a SpaceX shuttle mission to Mars at the moment: Thursday's earnings beat, which saw the company turn in its first ever profit, is no doubt a key factor behind the breakout performance. But given that Tesla's always been a heavily shorted stock there is potentially something of a short squeeze going on. Cue the following short interest chart from Markit: While the percentage of shares out on loan has fallen recently, it still stands at near 20 per cent. TSLA is also currently very expensive to borrow, with a cost to borrow score at a max of 10. According to Markit that means there's still a heavy short squeeze risk for the stock. In which case, here's hoping Tesla doesn't blow a fuse and turn into the stock that fell straight back to earth. Related links: Tesla's rise and the credit connection - FT Alphaville Elon Musk vs The New York Times - FT Alphaville Tesla drives California environmental credits to the bank - Los Angeles Times