Ed Rendell predicts Biden will clinch nomination

[George II]

7. According to the forecasts, Biden will win more than two-thirds of the delegates on Tuesday....

....and come out of the four states with 200 delegates more than Sanders. That would surge Biden to a 360+ delegate lead.

In other terms, Biden will need less than 50% of the remaining delegates to reach 1991, Sanders will need more 70% of the remaining delegates to reach 1991.

I.e., Sanders would need to win EACH of the remaining 26 primaries/caucuses with at least 70% of the vote. Inasmuch he hasn't won any of the previous 31 by that much - only five with more than 50% and only three with more than 60% (those three include his home state of Vermont and the delegate sparse Norther Marianas by 4-2!), it's virtually impossible for Sanders to ever get enough delegates to win the nomination.