Tuesday's Primary
Between now and the end of the primary season, I expect Sanders to pick up more delegates than Clinton, in total, by a very small margin.
On Tuesday, April 26th, there will be primaries in Connecticut, Delaware, Maryland, Pennsylvania and Rhode Island. That's 384 pledged delegates at stake.
Polls put Clinton ahead in all these states, but not all the polls are current and not all the Clinton leads are strong.
Added Note:
I noticed some very strong reactions in the comments section from people apparently (but not very clearly) accusing me of making up numbers to make it look like Sanders…