Warren moving up in the polls is no surprise. She's been churning out policy positions.
The sorting process among the top candidates in the polls won't begin in earnest until the first major debate. It's extremely early yet.
Warren hasn't been hammered the way she will be once the winnowing starts.
Sanders has vastly improved his foreign policy knowledge, and Tulsi Gabbard will make foreign policy and the anti-war movement much more visible once she speaks in the national debates.