VIKTOR ORBAN, Hungary’s autocratically inclined prime minister, suffered a string of political embarrassments recently. A referendum he heavily promoted on blocking the entry of refugees to the Central European country failed after a majority of voters heeded opposition calls to either stay away from the polls or spoil their ballots. Meanwhile, the country’s most important opposition newspaper was publishing exposés about corruption in his government, including the hiring by the central bank governor of his mistress and the use by the communications minister of a helicopter to attend a wedding.

On Oct. 8, publication of the paper, the 60-year-old Nepszabadsag, was abruptly suspended and its website was shut down. Its 50-odd journalists were locked out of their email accounts. Its owner of record, a Vienna-based businessman, blamed financial losses. But the journalists and their defenders in Hungary’s beleaguered opposition suspect the paper is the latest victim of Mr. Orban’s drive to stifle opposition and consolidate what he has called “illiberal democracy.” Though the ruling party denied responsibility, its co-chairman declared that “it was high time Nepszabadsag shut down unexpectedly.”

Control of the media has been a key strategic goal of Mr. Orban since his election in 2010. His government passed a media law imposing sweeping restrictions, but following scathing criticism from the European Union, of which Hungary is an increasingly fractious member, it has hesitated to enforce it. Instead Mr. Orban has acted more indirectly. State television channels have been turned into propaganda instruments, as has the state news agency, which now distributes its content gratis. Government advertising is used strategically to prop up pro-Orban publications while starving those that dissent.

As in Russia and Venezuela, some outlets have been bought by businessmen close to the government, who then turn them into official mouthpieces. Nepszabadsag’s journalists suspect that they may the victims of such a ma­nipu­la­tion, though they lack proof. They argue that the economic causes cited by their owner of record don’t add up: The company was said to be profitable just a year ago, and the staff and website of the newspaper had been expanded in recent months. A downturn could have been countered with layoffs or other cutbacks; instead the paper was shuttered days after embarrassing Mr. Orban’s propaganda chief.

The bottom line is that one of the last media outlets willing to expose corruption and challenge Mr. Orban’s abuses of power is gone. A country that belongs to two of the world’s most exclusive democratic clubs — the E.U. and NATO — now has only one major newspaper, one radio station, one television network and a handful of websites that offer critical coverage of the government. Mr. Orban is close to establishing his regime as an autocratic political alternative inside the West. He should not be allowed to succeed.