There are a fair number of myths about the 2000 presidential election, one of which concerns the campaign of Green Party candidate Ralph Nader. It has become a commonplace to say that Nader was a "spoiler" who splintered off enough progressive voters from Al Gore to enable George W. Bush to enter the White House.
That's not an accurate understanding of Nader's role in the campaign. Nader, in fact, nearly enabled Gore — who consistently polled behind Bush through the spring of 2000 — to win. (And, of course, Gore did win the popular vote.) Gore was unable to inspire voters. Nader's passionate pleas made progressives care about the campaign, and made them more concerned about stopping Bush than they would have been without Nader.
And this gets us to Bernie Sanders in 2016. Although most analysts believe Hillary Clinton will be the eventual Democratic Party nominee, the longer Sanders remains in the race may, in fact, be a benefit to Clinton if she is the nominee. That's because Sanders gives progressives passion about the election, something Clinton appears unable to do. And if Sanders manages to become the nominee, he may prove to be far more formidable than many Republicans believe.
Turmoil on the Republican side may make it irrelevant whether Democrats are inspired by their nominee, but if the GOP manages to unify around a credible candidate, Democrats will need all the passion they can muster. And Bernie Sanders gives them that passion, even if he doesn't end up as the nominee.