BUDAPEST — In less than two years as a member of the Hungarian Parliament, Timea Szabo says she has looked on helplessly as the ruling Fidesz Party has used its two-thirds majority to tighten its grip on the news media and the courts, redraw parliamentary districts in its favor and pack the constitutional court with supporters. On Jan. 1, a new “majoritarian” Constitution written and ratified by Fidesz takes hold.

“They are preparing the funeral for the Hungarian Republic,” Ms. Szabo said. Opposition groups, including Ms. Szabo’s small, green Politics Can Be Different Party, known by its Hungarian abbreviation L.M.P., have called for a demonstration on Friday against the “demolition of democracy” by Prime Minister Viktor Orban.

Democracy here is dying not with a single giant blow but with many small cuts, critics say, through the legal processes of Parliament that add up to a slow-motion coup. And in its drift toward authoritarian government, aided by popular disaffection with political gridlock and a public focused mainly on economic hardship, Hungary stands as a potentially troubling bellwether for other, struggling Eastern European countries with weak traditions of democratic government.

To mounting criticism from the European Union and the United States, Fidesz is racing to use its supermajority in Parliament to pass a flurry of legislation before the new Constitution takes effect, a push that critics say will consolidate overwhelming power with Mr. Orban, a political veteran who got his start opposing Communist rule as it waned in the late 1980s.