"... as political figures, they complement each other.
Sanders has the feisty populist vision and aura of incorruptibility that
Clinton so sorely lacks, while Clinton has the experience and
gimlet-eyed policy chops that have eluded Sanders in his many years of
howling in the political wilderness. Together, with Clinton suiting up
to take that 3 a.m.
phone call in the Oval Office while Sanders roams the country rallying
the troops and shaming the Republicans, they could make a pretty good
team." --Michael Bourne in Salon magazine today. Under normal circumstances, I would not favor asking a sitting U. S. Senator, in a body whose control is in question, to run for vice president, but a Clinton-Sanders ticket makes sense. Sanders' seat is safely left of center and he brings in a lot of voters who would either sit this election out or cast a protest vote for Donald Trump, shooting themselves in the foot to make an empty point. That vote would turn the Supreme Court over to the GOP for the foreseeable future.
Sanders is 74 and Clinton is nearly 70. Either or both could easily die during the next four to eight years, but it isn't likely both would fail to live through a revolutionary administration. The possibility of Sanders becoming president is much greater if he is VP than if he simply loses at the convention and goes away. As long as he hangs around--affecting policy the entire time--the longer the possibility of a Sanders presidency exists. This ticket would pretty put the Democrats in a relatively secure spot to win the presidency and from my angle, that looks much better than the alternative.