Politics: the 20% who think their party is too wimpy
According to RCP, Sanders is polling around 18% while Trump is getting 21%.
Does anyone really think either of these guys will become President?
The noise these two are making reveals the reality that within the two parties there are about 20% in each party who feel their party just doesn't get it and somebody needs to slap people around and shake things up.
On the Republican side, 79% want somebody other than Trump and unfortunately (or fortunately) depending on your political views that 79% is spread out among a whole bunch of relatively mainstream candidates who have won elective offices in their respective home states at some point of their political careers. Unless Trump totally self-destructs sometime soon, he will continue to bleed the party as an all too happy media covers him making a mockery of the GOP. At some point, some of the candidates will have to consider dropping out so two or three candidates become the viable ones easily distancing Trump in the primaries. But people running for POTUS are not known for putting their egos aside easily!
On the Democrat side, 82% want somebody other than Sanders. Fortunately (or unfortunately) depending on your political views, the bulk of that support belongs to Clinton. The worry for the Democrats is that some scandal that is brewing gains traction such that Clinton gets knocked out leaving the party with a scramble to find a truly viable candidate which Sanders is not.