So when a pro-government magazine, Figyelo, published a list of 200 Orban critics on Thursday, it was viewed as an ominous sign that he intended to make good on his threat.
The magazine labeled the people on the list — which included journalists and advocates at nongovernmental organizations — as “mercenaries” who were working to bring down the government. Many of them, it said, were under the command of the billionaire philanthropist George Soros.
Mr. Soros, a business magnate whose foundation funds pro-democracy groups, was born in Hungary and survived the Nazi occupation of Budapest before moving to England in 1947 and later settling in the United States.
Mr. Orban viciously attacked Mr. Soros throughout the campaign, and linked him to a central campaign tactic: stoking fear of immigrants and refugees, especially those from Muslim countries.
Mr. Soros, he said repeatedly, posed a threat to the country’s Christian identity and his goal was to “sweep away governments which represent national interests, including ours.”
Having won two-thirds of the seats in the Parliament — and with it, the ability to change the Constitution — Mr. Orban has promised to introduce a series of bills, labeled “Stop Soros” legislation, that would allow the government to penalize organizations supporting migrants.
The list published this past week also included a number of academics who teach at the Central European University in Budapest, which was founded by Mr. Soros.
In a statement, the university’s president, Michael Ignatieff, said that the list was “a flagrant attempt at intimidation that is dangerous for academic freedom and therefore for all of Hungarian academic life.”
The entire staffs of several nongovernmental organizations — including the Hungarian Civil Liberties Union, Amnesty International’s Hungarian section and the Hungarian Helsinki Committee — were also named on the Figyelo list.
The groups have vowed to carry on with their work.
“During its eight years in power, the government had already made it very clear that it values its own interests above the rule of law and democratic values, human rights and the Constitution,” the Helsinki committee said in a statement after the election.
At Saturday’s rally in Budapest, the crowd played off the nationalist themes of Mr. Orban and his allies. “We are the mercenaries,” read one sign, as people in the crowd sang the European Union anthem and waved E.U. and Hungarian flags.
The steady takeover of the Hungarian state by Mr. Orban has alarmed many members of the European Union, but the bloc has failed to stop Hungary’s drift from democracy despite threats of sanctions.
A draft report issued by the European Parliament on Thursday accused Hungary of undermining the independence of the judiciary, freedom of expression, and the rights of migrants and minorities. The report recommended the suspension of its voting rights, among other penalties.
But it is unlikely that sanctions will come to pass because they require a unanimous vote among member nations. Hungary and Poland, whose governing party has openly emulated Mr. Orban’s tactics, have vowed to protect each other from being penalized.
For now, the biggest threat to Mr. Orban’s party might be Hungary’s own citizens. While he secured a sweeping victory in the elections, which observers said were free but not completely fair, he still lost some 50 percent of the vote.
Ors Lanyi, 21, a student who had voted for the first time, was dismayed by a process that allowed a party that drew about half the vote to hold such sway in Parliament.
“I don’t want a one-party regime,” said Mr. Lanyi, who helped organize Saturday’s protest. “Obviously we need a new opposition — the one we have got reduced to nothing after those elections.”
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