Lawmakers in the House of Representatives who are trying to end the decades-old ban on U.S. crude oil exports said on Thursday they were gaining support after a Democrat joined the Republican-led effort. Representative Henry Cuellar became the first Democrat to sign on to a bill launched in February by Representative Joe Barton, a Republican and fellow Texan. "If we are able to lift the crude oil ban this is going to open up new markets where Texas businesses can create more jobs at home," said Cuellar, whose district includes the oilfields of Eagle Ford, where much of the U.S. boom in light sweet crude has been taking place over the last half decade.