and in 2016, he fundamentally changed politics in america. >> reporter: prior to his heart attack, the sanders campaign was stuck in neural, struggling to keep up with front-runners elizabeth warren and joe biden, but far ahead of lower-tier candidates unable to muster double-digit support. his heart attack threatened to draw 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 ilhan omar and appear later this monday with rashida tlaib, freshmen female members of congress.