Economist: MITT ROMNEYS charge that America had declared war on coal may not have won him last years presidential election. Yet this once-mighty industry is struggling, squeezed by the plummeting cost of natural gas and a torrent of tough new environmental rules. Last year 37.4% of American electricity production came from coal, down from 48.5% in 2007. The Energy Information Administration expects a slight rise this year as gas prices begin to creep up. But further restrictions on power-station emissions...