Bernie Sanders's presidential campaign has already taken a laser focus to topics Americans don't often hear raised by candidates on the trail, like climate change or money in politics. His other big focus — in fact, it's the first one listed on his website — is income inequality. Sanders tweeted Tuesday afternoon that "Income inequality kills":

All Americans are entitled to live health and decent lives. pic.twitter.com/VGNVjNFZN2 — Bernie Sanders (@SenSanders) June 2, 2015

What Sanders is referring to is that income dictates many of the opportunities for taking care of our health. His site describes a "rigged economic system" that rewards those at the top and leaves the have-nots without:

At a time when millions of American workers have seen declines in their incomes and are working longer hours for lower wages, the wealth of the billionaire class is soaring in a way that few can imagine. If you can believe it, between 2013 and 2015, the 14 wealthiest individuals in the country saw their net worth increase by over $157 billion dollars. We live in the one of the wealthiest countries on earth, yet children go hungry, veterans sleep out on the streets and senior citizens cannot afford their prescription drugs. This is what a rigged economic system looks like.

There are many facets to the topic, but here's one to think about, which draws a direct line between sickness and health. According to the Bureau of Labor Statistics, for example, the higher your income, the more likely you are to receive sick leave. Sick leave benefits are offered to 87 percent of income-earning Americans in the top 10th percentile of income. Only 20 percent of the bottom 10th percentile of income-earning Americans are offered the same benefits.

Sanders is an exciting candidate for many progressives because he raises topics that are avoided by most of his peers, and, as Matt Yglesias says, he is "free to just come out and say things that nobody making a serious bid for national office would say."