“Got to get back. Let me get through this,” Sanders said as he started five minutes of remarks laying out his rationale for running — amounting to taking on Clinton from the left.
Sanders has been pushing Wall Street reform for years, and taking on tax-dodging U.S. corporations has been one of his signature crusades.
With Sen. Elizabeth Warren, D-Mass., not running in 2016, Sanders has a chance to consolidate any anti-Clinton progressives and amplify their voices — to keep pressure on Clinton to pay close attention to them and their issues.
Though Sanders is a long shot, by running for president he gains a big stage for the next year, before the first 2016 presidential votes are cast in Iowa and New Hampshire.  http://chicago.suntimes.com/lynn-sweet-politics/7/71/567031/sen-bernie-sanders-challenges-clinton-dem-nomination-2
Bernie is not going to win but he will make thing both interesting and he will make Hillary squirm, especially if Sanders starts to get some votes.
Yep, Bernie will be Hillary's pain in the ass.