Monmouth’s poll finds that 41 percent of non-Biden voters would be “very” or “somewhat” likely to support him if he were to decide to run (a number that’s very close to Clinton’s 42 percent support, though we don’t have crosstabs to show how many Clinton backers would consider Biden). If Biden doesn’t decide to run, other polling suggests that it’s Clinton who will benefit from his not doing so – just as she’s the one who suffers when his candidacy is polled.
This is why Bernie Sanders Supporters should support a Biden run. Both Biden and Hillary Clinton share the same voter base. They will only cannibalize each other. This would mean that at the point Biden enters the race it would likely be a three way tie between Clinton, Biden and Sanders, at around 20% each.