To the outside world, Hungarian Prime Minister Viktor Orbán began his rule as a pariah—an obstreperous, often lone dissenter from European Union policies, especially over migration. Then he became a prophet to new-style “national conservatives”—the anti-immigration, anti-elite right-wing movement that has reshaped the politics of the West. After resoundingly losing national elections held on April 12, Orbán has become a parable for how populism can be defeated. His political demise was hardly inevitable. It had to be shrewdly engineered by politicians and voters who put aside their ideological differences to defeat him. In politics, there is no natural law of self-correction. From 2010 until now, Orbán and his Fidesz party transformed Hungary into a new kind of state, which he proudly proclaimed as an “illiberal democracy.” He and his allies rewrote the constitution to entrench his power, centralizing control over civil society and countervailing institutions such as courts and universities. Péter Magyar, the presumptive next prime minister, triumphed against a tilted electoral system—gerrymandered districts, government influence over traditional media and even over the country’s billboards—designed …