Both parties used to fight for the middle ground politically, back in the late 40's- mid 60's, before special interests and donors started pushing each side to their prospective corners. The left started going farther left and the right farther to the right because with the donor support they would receive more money to campaign, and more support from individual groups, be it the NRA or NAACP. The core of each party started getting more devisive and less representative of the American middle.
The middle ground is where the majority of voters are, but by staying with the middle, special interest groups don't get fast results regarding social change, like with LGBT rights for example. What you do get with staying with the middle politically, is lasting and accepted change with social issues that are more widely accepted. But, that is not a quick enough turn around time for big business or the special interest's to take advantage of.
What Trump and Sanders have done is to gain support from the middle, where the donor class, special interest groups, and professional politicians have forgotten "the people". The result of that is 40%+ of the electorate is fed up with the system that doesn't represent them, has no intention of representing them, and so the middle roaders are flexing their muscles, and bringing the political system back to where it doesn't want to go...putting average American's interests first.
It shows how twisted the process has gotten, when the media and insiders think that the two primary politicians who are bringing in the biggest crowds (Trump and Bernie) are horrible candidates with unworkable platforms. That is what the electorate would rather have this round, horrible platforms that are not run by special interests and donors, rather than the status quo that takes them for granted, or forgets the people altogether.
Conservatism is all but dead, Liberalism has become a PC joke, and the only way to get representation is to go with an outsider no matter how "bad" he is. This election is a rebuke of the political establishment of both sides, and the establishment still doesn't understand, or really want to address that there is a problem.
That is how Trump gains support, by laying it out how the people have been getting screwed, what the reasons are, and how he is going to take hard stances against those policies that aren't PC in the least. Basically going after middle of the road Americans who have been forgotten by design of the special interest and donor political process.
He's put the dividing lines between D and R where he wants them, and once Cruz finally is done and we are on to the general election, the field now is much easier for him to gain voters than it will be for Hillary, which is a good thing for our side.
