In Germany, fighting the far right poses a conundrum for democracy

For Germany — a country that knows something about how extremists can hijack a government — the surging popularity of the far right has forced an awkward question.

How far should a democracy go in restricting a party that many believe is bent on undermining it?

It is a quandary that politicians and legal experts are grappling with across the country as support surges for Alternative for Germany, a far-right party whose backing now outstrips each of the three parties in the governing coalition.

Not only is the AfD the most popular party in three states holding elections this year, it is polling nationwide as high as 20%. German politicians have become increasingly alarmed that someday the party could wield influence in the federal government. Its popularity has grown despite the fact that the domestic intelligence services announced they are investigating the...