The chart above is from the latest Morning Consult Poll -- done on March 5th of a national sample of 1,390 likely Democratic primary voters, with a 3 point margin of error.
The poll shows Joe Biden now has a large lead over Bernie Sanders of about 16 points (54% for Biden to 38% for Sanders). That's a huge change. Before South Carolina and Super Tuesday, Sanders was actually leading in this same poll.
Fivethirtyeight.com has also radically changed their primary prediction (see chart below). Just a few days ago, they were predicting a better than 60% chance that no one would get a majority of delegates. Now they are saying Joe Biden has an 87% chance of getting a majority of pledged delegates. There is 11% chance of no one getting a majority, and a 3% chance of Sanders getting a majority.
If Bernie Sanders means what he says, there will not be a brokered convention. A couple of days ago, he told Rachel Maddow that if Biden enters the convention with a plurality of delegates, then he should be the nominee