Is the Bernie Sanders campaign still accepting donations? Should they be? [View all]

Are people being misled into believing that just one more donation will help Bernie to get things going again? In one regard, I suppose that adults who are still donating to him are probably aware of the dire reality of his political situation. But on the other hand, I imagine that the adrenaline rush that people get after donating could be compared to the same rush from playing the slot machine... along with the belief that just ONE more try will turn the luck around... so they just keep feeding money into the machine and pulling the handle to spin the wheels, time and time again.

When a campaign has money left over, are they required to return it? Does the candidate get to keep it?