How much ground has democracy lost in recent years?

In China 30 years ago an audacious public protest in the capital's central square pushed the country's autocrats to the brink, and when the Soviet Union imploded, the ruling party's most relentless critic became Russia's president and dominant political figure. Ascendant America had no serious rival. In Europe, West welcomed East. Among the world's most advanced countries, there seemed little left to fight over. The end to a century of conflict appeared to ensure democracy had carried the day.
History had other plans. Today, most liberal democracies are more polarized than they've been in decades, and voters in the US, UK, France, Italy, Mexico, Pakistan and Brazil have rejected established political players in favor of hoped-for sweeping change. Political common ground between political parties in these and other countries is disappearing. According to Freedom House, a rights...