Rising gas prices are becoming a hot issue in the U.S. presidential campaign, as the cost of a gallon reaches as high as $2.39 in parts of the Midwest. George W. Bush and other Republicans blame the Clinton administration, saying the increases are being caused in part by clean air standards that require the sale of cleaner-burning reformulated gasoline in polluted areas. But Al Gore and administration officials say reformulated-gasoline requirements should raise prices by only four to eight cents a gallon, which wouldn’t account for recent drastic price increases. Gore is supporting an investigation into possible price gouging by oil companies, and his campaign is trying to portray Bush as beholden to the oil industry because of its substantial contributions to the Bush campaign. Meanwhile, some observers wonder whether there isn’t a silver lining to the higher prices because they could lower gas consumption, helping to alleviate pollution and global warming.