The start of July will mark one year since Pena Nieto’s election returned the PRI to power after a 12-years hiatus. Opening the energy industry to more private investment would be the “signature issue” for judging his presidency, Pena Nieto said during the campaign.

Pemex bondholders are losing confidence in his ability to achieve the needed changes after signs of fraying in the Pact for Mexico alliance that Pena Nieto engineered between his own PRI, the National Action Party, or PAN, of predecessor Felipe Calderon and the Democratic Revolution Party, or PRD.

“The PRD cannot sign on for an ambitious energy reform, and they’ve been quite explicit about that,” Duncan Wood, director of the Mexico Institute at the Woodrow Wilson International Center for Scholars in Washington, said in an interview. “It’s going to be very difficult for the elite of the PRD to continue working with the government if the government and the PAN push through an energy reform that they’re opposed to.”

Yields on $2 billion Pemex bonds due in 2022 jumped 72 basis points in the past month through last week to 3.97 percent. Yields on Brazilian oil producer Petroleo Brasileiro SA’s 2021 notes rose 63 basis points over the same period.