Tesla Motors is quietly about halfway from being a boutique auto maker selling a few hundred cars to being a major player with a U.S. market share over 1 percent. That analysis might have seemed like a stretch before the company’s latest earnings report, but that report this week pointed to a pace of sales roughly equivalent to a 0.25 percent U.S. market share, a big jump from the previous quarter. Future events that are easy to predict can be expected to at least double the company’s appeal: an expanded recharging network, a redesign of the most popular model for which a price cut is promised, more sales and service locations, and two or three years out, a new model with a less compact design. Unexpected events on the horizon may be just as significant, such as a spike in gasoline prices or a technological advance that makes the car battery smaller or lighter. If there is a faster increase in demand for Tesla’s electric cars, the automaker is in a position to meet it. It is the owner of a large, mostly vacant factory that, combined with its robotics-driven approach, looks sufficient to take it, perhaps just as quietly, to a market share above 10 percent. That can happen, of course, only if events intervene to give electric cars some new advantage over gasoline-burning cars. But, given the recent history of troubles in Detroit and in the oilfields, along with the steady march of changes in electric technology, such a turn of events would not be too surprising.