At this point Bernie Sanders seems to have become a liability for the Democrats.
Sanders likely can't capture enough delegates to win the nomination. To illustrate, Clinton currently has a 39 % delegate lead over Sanders (super-delegates not included), which is in no way as close as the race between Obama and Clinton in 2008, where Obama led by only 7 % in March 2008.
https://en.wikipedia.org/wiki/Democrati ... 2008#March
Yet Sanders can't lose so decisively - so far - that the Clinton nomination can be considered a foregone conclusion, either. As such, the Democrats need to waste effort and money on campaigning against Sanders (who will likely lose anyway) instead of campaigning against the GOP.
The polls suggest that Clinton will defeat Sanders across the board on March 15, including the (likely) most important state: Florida. However, the polls also incorrectly predicted a victory for Clinton in Michigan (with a whopping 20 point margin, even), so I guess we'll just have to see what happens next week.