Venezuelans are casting their votes in gubernatorial elections expected to be a gauge of support for a fractured opposition and of President Nicolás Maduro’s grip on power in a country crippled by severe economic and political crises.

Polls suggest opposition candidates could win more than half of the 23 governor seats, but Maduro critics claim that government-friendly electoral officials have twisted voting procedures to favour official candidates.

The opposition coalition, which led months of anti-government protests this year in which more than 120 people have been killed, is hoping for a massive turnout, as polls show that most Venezuelans are deeply disenchanted with Maduro and the ruling socialist party.

“If the vote were to be completely free and fair, the [opposition coalition] would likely win between 18 and 21 states,” said Risa Grais-Targow, an analyst with the consultancy firm Eurasia Group.

According to polling by Datanalisis, the government candidates are on 21% of the vote, while opposition and independent candidates are on 62%.

Last week, the US Department of State expressed “great concern” over moves by Venezuela’s electoral council that it said called into question the fairness of the electoral process.

In what appeared to be an effort to keep many opposition supporters from voting, the government-friendly election body announced it was moving 205 polling stations from some neighbourhoods where the opposition support is high to mostly poor, violence-plagued barrios that are seen as Maduro strongholds. It also included on the ballot the names of opposition politicians who lost in primary elections. A vote for any of the non-candidates would be not counted.

The socialist party and the president have come under increasing international pressure after a crackdown on protests and the creation of a new constitutional assembly, which given them absolute control. The assembly has been ruling practically unchecked since being elected in July in a vote boycotted by opposition parties.

Maduro has been described by many world leaders as a dictator. In a speech on Saturday, he said Sunday’s elections would be an achievement of Venezuela’s “revolutionary democracy and socialist democracy”.

Grais-Targow said that while the Maduro administration was willing to hold the election in attempt to temper international pressure, it was “nevertheless trying to diminish their margin of defeat by throwing down multiple obstacles to undermine the opposition’s vote”.

Divisions among the opposition could also hurt Sunday’s turnout. Fearing that their participation in the election legitimises the government, some factions refused to put up candidates, or are refusing to to cast their ballots.

“I am not going to vote. But I think every Venezuelan should do what their conscience dictates,” said María Corina Machado, a former national assembly member, told local media.

Venezuelans are suffering a crippling recession, now into its fourth year. It has driven many into poverty amid the scarcity of basic foods and medicines. The International Monetary Fund has described the situation as “a full-blown economic, humanitarian, and political crisis with no end in sight”.

By the end of year, the Venezuelan economy will have shrunk by 35% since 2014, according to the IMF.