GEORGETOWN, Guyana — The old tensions are rumbling again.

Three years ago, Guyana attempted to set aside decades of ethnic divisions when it voted in a multiracial governing coalition that gave voice to a new generation of politics.

With a promising discovery of oil offshore around that time, the future suddenly looked brighter for a country where most college-educated people emigrate to the United States, Canada and Britain.

But old habits have proven hard to break.

The political party that held power for 23 years, before the new coalition was voted in, is already accusing the government of stacking the decks for the national election in 2020. Government preparations for the first oil production in the country’s history are going slowly. And promised investigations into past corruption by successive governments have floundered.

“We thought they would change everything, but they didn’t change anything,” Clement Dhanpat, a farmer of Indian descent, said as he walked out of a rice field on a recent day after spreading fertilizer.