There is a powerful reason that automakers worldwide are speeding up their efforts to develop electric vehicles - and that reason is China. Propelled by vast amounts of government money and visions of dominating next-generation technologies, China has become the world's biggest supporter of electric cars. That is forcing automakers from Detroit to Yokohama and Seoul to Stuttgart to pick up the pace of transformation. Beijing has already called for one out of every five cars sold in China to run on alternative fuel by 2025. Last month, China issued new rules that would require the world's carmakers to sell more alternative-energy cars here if they wanted to continue selling regular ones. China has reshaped industries before. This, however, would be on a different scale. If China succeeds - and there is no guarantee - Beijing's policy makers will be front and center reimagining the global auto industry. Already, China is the world's largest maker and seller of electric cars. Chinese buyers are on track to snap up almost 300,000 of them this year, three times the number expected to be sold in the United States and more than the rest of the world combined. The country's market heft is considerable. China buys more General Motors-branded cars than Americans do. Even for Tesla, the still-small American maker of luxury electric sedans, China has become the second-largest market, even though China's taxes on imported cars are 10 times as high as those in the United States.