tonight, the biggest showdown so far, the fight for 2020, joe biden verses elizabeth warren. the democratic front-runners face to face for the first time in the debate stage tomorrow night, this as the new cnn poll tonight shows biden s lead over warren, should rinking dramatically. they re now six point apart. that was 15 points just one month ago, okay? that s dramatic and so we are learning new details about biden s plan of attack to change that narrative. according to one adviser he s going straight for warren and her plans. jeff zeleny is out front. in the human brain, billions of nefor people with parkinson s, reporter: joe biden is some neurons change their tune, nothing, if not resilient. tonight, a new cnn poll shows causing uncontrollable tremors. biden leading the field at 24%. now, abbott technology can target those exact neurons. with elizabeth warren and bernie sanders locked in a tight race for second. restoring control and harmony, biden s advantage comes from his o