On immigration, both Trump and Sanders sound restrictionist notes. Trump rose to political prominence in part with his comments accusing Mexico of sending criminals and rapists to the United States. Sanders warns that immigration depresses American wages and contributes to youth unemployment.

On trade, Sanders and Trump both oppose the North American Free Trade Agreement (NAFTA) that was one of President Clinton’s great achievements. Trump called NAFTA a “disaster” and Sanders described it as a scheme to allow “multinational corporations” to “exploit desperate third world workers.” They also oppose the Trans-Pacific Partnership agreement. Hillary Clinton helped to craft that agreement as Secretary of State (though she has been noncommittal about it as a candidate). Governor Jeb Bush, by contrast, is a big supporter of free trade.

On guns, Sen. Sanders was initially elected to Congress with the support of the National Rifle Association. Pro-gun-control journalists denounce him as a “gun nut.” Trump, likewise, has been running on what he describes as a strong pro-Second Amendment stance.

Even the personal lives of Mr. Sanders and Mr. Trump have certain similarities.