between a plan and a pipe dream is something you can actually get done. >> reporter: senator amy klobuchar also criticizing her health care plan. >> no one wants to protect billionaires. not even the billionaire wants to protect billionaires. we just have different approaches. >> reporter: the massachusetts senator fighting back. >> i think as democrats we're going to dream big when we fight hard, not when we dream small and quit before we get started. >> reporter: warren, not the only candidate on their heels. joe biden defending his son hunter's work in the ukraine in the wake of the scandal rocking washington. >> my son did nothing wrong. i did not wrong. i carried out the policy of the united states government in rooting out corruption in ukraine. >> reporter: biden explaining why he believes he's trump's target. >> he's going after me because he knows if i get the