The future of Venezuela is on the line. Voters will decide Sunday whether to reelect President Nicolas Maduro, whose 11 years in office have been beset by crisis, or allow the opposition a chance to deliver on a promise to undo the ruling party’s policies that caused economic collapse and forced millions to emigrate.

Historically fractured opposition parties have coalesced behind a single candidate, giving the United Socialist Party of Venezuela its most serious electoral challenge in a presidential election in decades.

Maduro is being challenged by former diplomat Edmundo González Urrutia, who represents the resurgent opposition, and eight other candidates. Supporters of Maduro and Gonzalez marked the end of the official campaign season Thursday with massive demonstrations in the capital, Caracas.

Maduro and his allies have traditionally fended off challenges by barring rivals from elections and painting them as out-of-touch elitists in league with foreign powers. But this time, the ruling party is allowing the Unitary Platform, the coalition of the main opposition parties, to participate in the election.

A deal that allowed the opposition coalition to participate in the election won Maduro some relief from crippling economic sanctions imposed by the United States. But that respite was short-lived. President Joe Biden’s administration re-imposed the sanctions, citing mounting government repression of real and perceived adversaries, including blocking the candidacy of opposition powerhouse María Corina Machado.

Here’s what to know about Venezuela’s upcoming presidential election.

Who is the opposition candidate?

The most talked-about name in the race is not on the ballot: María Corina Machado. The former lawmaker emerged as an opposition star in 2023, filling the void left when a previous generation of opposition leaders fled into exile. Her principled attacks on government corruption and mismanagement rallied millions of Venezuelans to vote for her in the opposition’s October primary.

But Maduro’s government declared the primary illegal and opened criminal investigations against some of its organizers. Since then, it has issued warrants for several of Machado’s supporters and arrested some members of her staff, and the country’s top court affirmed a decision to keep her off the ballot.

Yet, she kept on campaigning, holding rallies nationwide and turning the ban on her candidacy into a symbol of the loss of rights and humiliations that many voters have felt for over a decade.

She has thrown her support behind Edmundo González Urrutia, a former ambassador who has never held public office, helping a fractious opposition unify.

They are campaigning together on the promise of economic reform that will lure back the millions of Venezuelans who have migrated since Maduro became president in 2013.

González began his diplomatic career as an aide to Venezuela’s ambassador in the U.S. in the late 1970s. He was posted to Belgium and El Salvador, and served as Caracas’ ambassador to Algeria. His last post was as ambassador to Argentina during Hugo Chávez’s presidency, which began in 1999.

More recently, González worked as an international relations consultant and wrote a historical work on Venezuela during World War II.

Why is the current president having trouble?

Maduro’s popularity has dwindled due to an economic crisis caused by a drop in oil prices, corruption and government mismanagement.

Maduro can still bank on a cadre of die-hard believers, known as Chavistas, including millions of public employees and others whose businesses or employment depend on the state. But the ability of his party to use access to social programs to make people vote has diminished as the economy has frayed.

He is the heir to Hugo Chávez, a popular socialist who expanded Venezuela’s welfare state while locking horns with the United States.

Sick with cancer, Chávez handpicked Maduro to act as interim president upon his death. He took on the role in March 2013, and the following month, he narrowly won the presidential election triggered by his mentor’s death.

Maduro was reelected in 2018, in a contest that was widely considered a sham. His government banned Venezuela’s most popular opposition parties and politicians from participating and, lacking a level playing field, the opposition urged voters to boycott the election.

That authoritarian tilt was part of the rationale the U.S. used to impose economic sanctions that crippled the country’s crucial oil industry.

Who will vote?

More than 21 million Venezuelans are registered to vote, but the exodus of over 7.7 million people due to the prolonged crisis — including about 4 million voters — is expected to reduce the number of potential voters to about 17 million.

Voting is not mandatory and is done on electronic machines.

Venezuelan law allows people to vote abroad, but only about 69,000 voters met the criteria to cast ballots at embassies or consulates during this election. Costly and time-consuming government prerequisites to register, lack of information and a mandatory proof of legal residency in a host country kept many migrants from registering to vote.

Venezuelans in the U.S. face an insurmountable obstacle: Consulates, where citizens abroad would typically cast their ballots, are closed because Caracas and Washington severed diplomatic relations after Maduro’s 2018 reelection.

Under what conditions is the election taking place?

A more free and fair presidential election seemed like a possibility last year, when Maduro’s government agreed to work with the U.S.-backed Unitary Platform coalition to improve electoral conditions in October 2023. An accord on election conditions earned Maduro’s government broad relief from U.S. economic sanctions on its state-run oil, gas and mining sectors.

But days later, authorities said the opposition’s primary was against the law and began issuing warrants and arresting human rights defenders, journalists and opposition members.

A U.N.-backed panel investigating human rights violations in Venezuela has reported that the government has increased repression of critics and opponents ahead of the election, subjecting targets to detention, surveillance, threats, defamatory campaigns and arbitrary criminal proceedings.

The government has also used its control of media outlets, the country’s fuel supply, electric network and other infrastructure to limit the reach of the Machado-González campaign.

The mounting actions taken against the opposition prompted the Biden administration earlier this year to end the sanctions relief it granted in October.