Remove Republicans and you haven’t completely eroded Gabbard’s base. The data you showed also demonstrates Gabbard is drawing independents. Where Trump, Sanders and Gabbard intersect is on global isolationism.
So what if Republicans don’t represent the entirety of her support, they represent the majority of it which was my point. She’s the strong favorite of people who aren’t going to support the democratic nominee anyway and so if people are wondering where her newfound support came from that answers the question.