Midterm elections in Mexico, as in the United States, are a referendum on a president’s performance.

On Sunday, Mexicans will elect an entirely new Congress along with 17 state legislatures and a host of governors and mayors. The results will set the tenor for President Enrique Peña Nieto's final three years in office.

The new Congress will support — or stall — legislation in the second half of Peña Nieto’s term. And the election outcome has implications for United States-Mexico relations.

Congressional representatives in the lower Chamber of Deputies are limited to a three year term. Senators serve a single six year term as does the Mexican president.

After a 12 year absence, Peña Nieto led his PRI party back to Los Pinos — Mexico’s White House — three years ago pledging to change the national conversation.

Peña Nieto hyped economic and political reform, and Mexicans loved the message.

He arrested the corrupt head of the politically powerful teachers union and he was crafting energy and telecommunications reform, in an unprecedented attack against state and private monopolies.

He said he’d confront corruption head on. But today, opposition election ads focus on one theme.

"Zero tolerance for corrupt politicians" is exclaimed in an opposition party's radio ad. The message castigates Peña Nieto, saying his rhetoric has been hollow and cosmetic.

His presidency has been tarnished in the last year by violence and evidence of continuing corruption.

Last September — in the most shocking incident — 43 students were taken off buses in a small town in southern Mexico and murdered, allegedly on orders from an elected mayor. The mayor is accused of ordering his local police to hand the students over to assassins, who may have been told the students were members of a rival cartel.

In April, criminals murdered 15 police officers, shot down a military helicopter and set at least 15 banks on fire. One news report in Mexico called it an "unprecedented attack."

And in May, the government was again on the defensive, after a shootout that left 42 purported cartel members and one policeman dead.

The violence has also tarred the elections themselves. Four candidates for office have been killed. Those include two candidates running in mayoral races in the southern states of Michoacan and Guerrero.

“Making change without spilling blood isn’t easy,” said Raul Acosta, a retired political science professor, in Spanish.

Acosta said Peña Nieto’s predecessor Felipe Calderón also wanted change that ended in violence. Calderón thought he could stabilize Mexico by confronting organized crime. It didn’t work.

The violence seen today has its roots in Calderón’s war. Now, Acosta says the biggest obstacle facing all parties isn’t disdain. It’s apathy.

"People have no motivation to vote," he said. "There's general discontent out there."

Roberto Grado, a local leader of the opposition PAN party in Chihuahua, agrees.

“People are despondent," Grado said in Spanish. "They don’t have faith in any political party."

That’s also because in the last three years, there have been a series of allegations of corruption raised against every party.

The voices of political analysts are echoed by people on the streets of this northern Mexico state.

“I don’t trust them. They’re all the same," said clothing distributor Salvador Andrade of politicians in general.

His worst fear, he said, is that nothing will change, that the status quo is unchallenged and that violence and corruption continue to scar Mexico.

“I’m afraid of what’s going to happen,” he said looking ahead to Sunday's vote.

In some states, some voters have said they will not participate in the election. And in some regions, election supervisors have said they are afraid to staff polling stations because of actual or implied threats of violence from any number of disaffected interests.

There’s currently a movement to annul or destroy votes by leaving ballots unchecked. Activists have blocked roads urging drivers to annul their votes to signal dissatisfaction.

Andrade doesn’t like that strategy.

“Our vote is the most important weapon that we have to change this situation," Andrade said.

Turnout in midterm elections in Mexico is notoriously low, and this time around may be even more so. National polls suggest flagging support for Peña Nieto.

“There is a story here for us in the United States," said Andrew Seeley, a Mexico and Latin America specialist at the Woodrow Wilson International Center for Scholars in Washington, D.C.

Seeley said there are fundamental questions the U.S. hopes are answered on Sunday.

“Is Peña Nieto going to come out of this election strengthened? Is he going to come out being seen as a leader who has a mandate, who has control of Congress?" Seeley said.

"In that case he’s in a very strong position to look at some of the international issues, including issues of economic opening with the United States, issues with migrants in the United States and lot of things that have to do with our country."

There are other issues of importance to the U.S. For one, American energy companies are also monitoring this election campaign. They’re eager to enter Mexico’s domestic energy sector.

Peña Nieto helped change Mexico’s constitution to allow foreign companies in. He overcame Mexican nationalists who say outsiders have no place in Mexico’s energy market. If he comes out of this midterm politically weakened, Peña Nieto will be forced to focus on building coalitions rather than on attracting foreign businesses.

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