Thus far, the primaries for both the Democratic and Republican parties feature surprisingly strong performances from candidates considered to be at the extreme of their respective ideologies. In the GOP, Donald Trump’s “straight talk” has him polling consistently ahead of the more established politicians in his party. For the Democrats, self-proclaimed socialist Bernie Sanders has capitalized on Hillary Clinton's stumbles to take the lead in New Hampshire polls and gained in other key states. One would expect the ultra-conservative Trump and uber-liberal Sanders to be at opposite ends of the political spectrum, but they share common stances on a surprising number of issues; they are strict on immigration and opposed to international free trade and gun control, among other things.
That's because Sanders and Trump are the left and right heads (respectively) of the same coin — populism. It's a movement whose name you may recall from high school history courses for its popularity during the early twentieth century. Populists believe that the "average" person should have more control of politics and the economy, and that some force is improperly taking that control away. By definition, a populist champions the middle class against those that are trying to destroy it.
For Sanders that enemy is "the one percent." Per Sanders, the wealthy are hoarding all the resources in America, and all the growth in those resources that the common man works for. The common man wants to combat this and the government should be his/her ally in doing so, but the rich are paying off the government through their campaign contributions to keep the government out of their way.
Trump rallies against immigrants. His campaign website "positions" section should really be changed to the singular, since the only stance listed is immigration reform. According to Trump, we must deport millions of immigrants because they're drug dealers, criminals and rapists. These violations perpetrated against "real" Americans are icing on the cake after these immigrants have already stolen good American jobs.
Of course, Sanders won't tell you that the actual numbers suggest that social mobility is the same now as it was for our parents and their parents, or that even the lowest classes in the US have higher standards of living than most people on the planet. Trump won't admit that immigrants who pay taxes but don't receive welfare benefits are almost single-handedly propping up our Social Security system or that immigrants are actually less likely to commit violent crimes than their American-born counterparts. These facts ruin the false narratives advanced by the angry orators.
Populism made its first appearance one hundred years ago because people were dissatisfied with a broken political system and needed someone to blame. It has again reared its ugly head for the same reason as politicians search for easy scapegoats to blame for all our problems. Yes, problems exist. Yes, the political mainstream has failed to address them (and has probably even exacerbated them), but attacking individual groups will do little to solve them. The populist position appeals to frustration and anger, and not only damages the target of their rage, but also pulls time and energy away from finding a real solution. If we really want to fix America, then the first step is to stop feeding the egos and campaign funds of the trolls.