KATY, Texas — As Democrats try to win control of the US Congress in next year’s midterm elections, their hopes of picking up a Senate seat in Republican-dominated Texas rest with a telegenic ex-punk rocker who wants to impeach President Donald Trump and legalize marijuana. Beto O’Rourke’s long-shot bid to unseat incumbent Republican Senator Ted Cruz illustrates the tightrope Democrats must walk as they gear up for the November 2018 elections. Democrats will have to win in areas that backed Trump last year in order to gain control of the House of Representatives and the Senate but even in Texas the party’s left-wing base is pressing candidates to stop the president by any means necessary. O’Rourke, who currently represents El Paso in the House, is drawing big crowds across Texas as he calls for universal healthcare and new restrictions on gun ownership. At a recent rally outside Houston, hundreds of supporters stood in line for up to an hour to shake his hand. O’Rourke, 45, said Trump’s surprise victory last year was a big reason he decided to run for the Senate. He said Trump’s racially charged rhetoric and divisive governing