Like Trump, Sanders is tapping into a seething discontent in American life over who has power and who doesn’t. AUSTIN, Texas — At a massive Bernie Sanders rally like the one held downtown here on Sunday evening, you get the sense that a huge swath of the Democratic voter base is deeply unhappy with everything in America, and has been for a while.The immediate object of their ire might be Donald Trump, but their discontent goes further back than the last election, and it encompasses more than politics as usual. They want everything Sanders promises: Medicare for all, free college,...