A NDRéS MANUEL LóPEZ OBRADOR , who became Mexico’s president on December 1st, knows how to put the romance into a honeymoon. On December 13th thousands of people attended a free moonlit screening of “Roma”, a Mexican film tipped for an Oscar, next to the heliport of Los Pinos, the residence of Mexico’s presidents until Mr López Obrador took over. The culture ministry supplied popcorn and punch. Mr López Obrador, or AMLO , as he is known, has swapped Los Pinos for more modest digs and opened it up to the public.

Rocio Bonilla, a retired civil servant, watched with her 86-year-old mother, who remembers the first presidential occupant of Los Pinos, Lázaro Cárdenas, who took office in 1934. “I never thought I’d be allowed to come here,” says Ms Bonilla.

While Mexicans huddled under blankets at the heliport, AMLO was making the sort of decisions that can eventually spoil a honeymoon. The veteran left-wing populist has begun to undo reforms of energy and education, the two landmark achievements of his predecessor, Enrique Peña Nieto. Before the inauguration he spooked the financial markets by saying that he would stop Mexico’s biggest infrastructure project, a new airport for Mexico City. At the same time he is travelling about the country launching others, including a tourist train in southern Mexico and a refinery in his home state of Tabasco.

On December 15th AMLO presented a budget for 2019, giving Mexicans their first idea of the trade-offs he is prepared to make in pursuit of his “fourth transformation” of Mexico, which is supposed to uplift the poor, make the economy more self-sufficient and reduce corruption and crime. The budget shows that AMLO remains a populist, but that he hopes to be a fiscally responsible one.

After the fright he gave the markets by cancelling the airport (in response to a spurious vote badged as a “consultation” of the people that he held before taking office), AMLO sought to reassure investors. The finance minister, Carlos Manuel Urzúa, set a target for a primary surplus (ie, before interest payments) of 1% of GDP after an expected 0.8% this year. Although AMLO had suggested that preventing corruption would result in massive savings, the budget does not rely on that unrealistic promise. Instead, he had to make some hard choices. He has scaled back his plans for higher social spending, although these remain ambitious. He is speeding ahead with high-profile infrastructure projects, which cost less money. And he is bringing back the idea that the state should provide energy that is abundant and cheap.

He had planned to spend 125bn pesos ($6.2bn), about 0.5% of GDP , on scholarships for the young. That programme will get a little more than a third of that. The budget allocates 60bn pesos of new money for a universal pension for old people, 20bn pesos less than originally proposed. To help pay for these still-large programmes the government will slash elsewhere, in some departments by more than 20%.

An overhaul of migration policy will get little money. Marcelo Ebrard, the foreign minister, announced spending of $5bn a year to discourage migration from Central America to the United States—partly to please President Donald Trump. This seems to be a repackaging of other promises to spend money in southern Mexico.

The austerity will not affect AMLO ’s favourite infrastructure projects. On December 16th he attended an indigenous ceremony (pictured) in which he asked “Mother Earth” for permission to build the “Maya” tourist train. (Mother Earth’s advocates in government have yet to be consulted. No environmental impact report on the project has been published; the budget cuts funding for the environment ministry by a third.) AMLO is eager to start work on the refinery. The budget includes 73bn pesos in extra funding for Pemex, the state-owned oil company, largely to pay for it.

This is part of his expensive scheme to make Mexico self-sufficient in energy. AMLO ’s government has not torn up contracts already agreed with international oil companies, an important part of Mr Peña’s energy reform. But it plans to freeze auctions of rights to prospect for oil and gas for three years. AMLO hopes to cut fuel prices once the new refinery is built. Pemex, which has a history of inefficiency and corruption, is supposed to raise oil production by 50% during his six-year term.

Congress, which is dominated by AMLO ’s Morena party and its allies, is debating measures to scrap Mr Peña’s education reform, which sought to enforce higher standards of teaching in Mexico’s terrible schools. AMLO wants to make education free at all levels.

The costs of reversing Mr Peña’s reforms will become visible only gradually. The government risks wasting billions in AMLO ’s attempt to restore to Pemex some of the glory it lost when Mr Peña ended its monopoly of oil extraction. Cuts to fuel prices will eventually burden the budget. Weaker accountability for teachers will lead to poorer performance by pupils.

The attempt to end the $13bn airport is causing immediate problems. Work on the doomed project continues, because the state-owned airport trust will have to repay $6bn of bonds when it is cancelled. It does not have the money, and AMLO does not want to pay out of the budget. Bondholders rejected an offer by the government to buy back a third of the bonds at a discount, and are unenthusiastic about a more generous offer. Until a solution is found, the cranes must continue to operate.

Continued construction of the airport and AMLO ’s conservative budget have soothed investors for now. But the calm may not last long. The budget assumes that the economy will grow by 2% next year, but some private-sector economists expect the increase to be smaller. A sharp drop in oil prices would upset the calculations on which the budget is based.