stuck in neural struggling to keep up with front-runners elizabeth warren and joe biden, but far ahead of lower-tier candidates. his heart attack drawing in new questions about his age and fitness for office but his supporters said they weren't worried about it. >> he is okay. that is the last thing i'm thinking about. he will be around here at least another 30 years. >> reporter: sanders is working to solidify support from the progressive left. in addition to locking up ocasio-cortez he picked up the endorsement of omar and appear later this monday with rashida tlaib, freshmen female members of congress. >> i am in the united states congress now. and that is a long, long way from being sexually harassed