Bernie Sanders and Ted Cruz are extremists. Their supporters don't like that label, but that doesn't mean it's not true.
Sanders is an extremist of the left, while Cruz is an extremist of the right. Both of them (and their supporters) are convinced that a majority of Americans would agree with their extremist views -- if only the media would help them get their message out. They are both wrong.
There has been plenty enough media coverage of both for the American public to know where they stand on the issues. Americans now know who these candidates are and what they believe. They just don't want what these men are selling.
It is just a fact that the great bulk of American voters are moderates. Extremism scares them -- whether it comes from the right or the left. The country moves slightly to the left or the right at different times, and after a few presidencies, tends to move the other way. But they almost always reject overwhelmingly a candidate of either party that is too extreme. Just look at what happened to Barry Goldwater or George McGovern. Both were viewed as extremists, and both were soundly defeated.
This does not mean that American voters don't want change. They do. They just don't want extreme change. They don't want to upset the apple-cart -- just make that cart a bit better. They understand that the system is out of whack right now, and has been tilted to favor the rich -- but they also understand that the system has been good for this country, and can be made fairer without radical changes. Americans want their change to come in steps, with each step being evaluated before moving to the next. That may not make the extremists in either party happy, but it is the way things are in this country.
And it is not just the general public that feels this way. Note that neither Sanders nor Cruz have been able to outright win the nomination of their respective political parties. The Democratic Party is not an extremist party of the left. It is a moderately progressive party. And while the Republican Party is solidly a right-wing party, it is not an extremist far-right party. That's why both parties have rejected their most extreme candidates (Sanders and Cruz).
This is not to say that Sanders and Cruz don't have their supporters. They do, and those supporters are passionate about their candidate. But those supporters are a minority, and they need to realize that now that the presidential campaigns are winding down. I don't know if they'll stick with the party of their chosen candidate, or vote third party or stay at home on election day. I just know that the American people, as a whole, will vote for the candidate who best represents moderate change in November.
(NOTE -- The caricatures of Sanders and Cruz above are by DonkeyHotey.)