MEXICO CITY — Many Mexican politicians are losing sleep lately pondering an enigma: How is it possible that the most important set of governmental reforms in decades has aroused so much enthusiasm abroad and yet so much rejection in Mexico? How is it that, while the groundbreaking reforms were approved by a two-thirds majority of Congress, ordinary Mexicans affirmed in a poll that they believe their country is moving in the wrong direction?

Some observers have compared the scope of Mexico’s reforms with American legislation to combat monopolies initiated by Theodore Roosevelt early in the 20th century. Roosevelt’s program put formal limits on the ownership of railroads, mines, oil resources, and steel and tobacco production. President Enrique Peña Nieto, in the 21 months he has been in office, has set limits on the state’s longstanding monopoly on the extraction, production and distribution of oil, gas and electricity by permitting private investment; he has diminished the power of the telecommunications giants Telmex and Televisa by opening the door to competition; and he has compelled the huge National Union of Education Workers to accept reforms that prohibit the sale or inheritance of teaching positions and that introduce compulsory exams to evaluate teachers.

For Mr. Peña Nieto and his team of old-guard politicians and young technocrats, these reforms were a top priority, especially as the government risks losing its legislative majority in the interim elections next July. The legislation is all the more significant because it was pushed through as a grand “Pact for Mexico” via a previously unthinkable deal with the major opposition parties. So why is practically no one celebrating the president’s achievement?

One answer lies in the bitter experiences of Mexico’s recent history.

Toward the end of the 1970s, the discovery of huge oil deposits in the Gulf of Mexico led President José López Portillo to promise the Mexican people an “administration of abundance.” A wave of hope swept the country. But these vast resources were siphoned off into an ocean of waste, bad investments and corruption. The reckoning came in 1982 with Mexico’s financial bankruptcy. Reforms subsequently put in place during the administration of Carlos Salinas de Gortari (1988-1994) were undermined by political scandals and violence, and then a series of economic errors provoked a second financial collapse.