The power behind the throne
I didn't know about the Biden family tragedies or Joe Bidens' age, but I had a feeling he wouldn't enter the US Democratic election race.
While everyone was going on about the big fight, in the background was the idea that Mr. Biden may enter as a latecomer. The longer this went on, the more likely I thought it wouldn't happen.
While the President is the public face of power, the real power lies with the person backing him/her.
As much as supporting the President, the VPs job is to "run interference." Any ex-service personnel will tell you It's the NCOs who run the establishment.
In recent history, you only have to review the protection Hilary Clinton gave her husband over the scandals. If the VP loses confidence in the President, they have the power to cause massive disruptions.
To understand this better, look at the current US Presidential election. Hilary Clinton was counting on Joe Biden not to enter; she knew if he did enter the race, her followers would flock to his side. What she didn't expect was for Mr. Biden to abstain, and attack her policies in the press. With Bernie Sanders beating her in the polls, despite what the press say http://hereiamattheedge.blogspot.co.uk/2015/10/1990.html#.VijjzlUViko The main thing to remember is that her backers report the polls showing Mrs. Clinton in the lead. Mrs. Clinton required the votes of the Biden supporters to give her a hope of winning - that looks doubtful now.
The VP rarely leaves the country, so they have their finger on the pulse of the people. As much as people vote for the party, the VP is an intrinsic part of the equation. Belief in the VP is as vital as belief in the party policies.
If the VP gets in trouble, all they need do is say I was doing as I was told.