Swing-state voters have, judging by the polls, mostly rejected the darker insinuations about Barack Obama’s background. But they sure have taken hold in Texas, where a University of Texas poll shows a full 20 percent believing that Obama is a Muslim. That makes it one red state Obama won’t be winning. Another 28 percent could not identify his religion. But there is one intriguing finding in the poll: Only 34 percent approve of George W. Bush.