Turkey will go to the polls on Sunday to vote in general elections that could have a historic impact on the republic's political system, and perhaps even its future as a functional democracy. But the results will be close, and tens of thousands of volunteers have signed up to monitor the vote amid fears that the process will not be free and fair.

President Recep Tayyip Erdogan is hoping that the ruling Justice and Development Party (AKP) — which he headed as prime minister for three terms — will gain the majority needed to make a constitutional change that will vastly increase his powers and allow him to further shape the country to his vision.

Standing in the way is the pro-Kurdish People's Democratic Party (HDP), which is aiming to exceed the 10 percent vote threshold required for a parliamentary presence. An HDP victory would block the AKP from holding the 330 parliamentary votes (out of 550 total) required for constitutional change. The notoriously inaccurate Turkish opinion polls are split on whether the HDP will land above or below the key 10 percent figure.

Meanwhile, trust in the electoral system is declining, and 43 percent of eligible voters think Sunday's polls will not be fair, according to a study published last month by professors Ali Carkoglu and S. Erdem Aytac of Koc University. In response, volunteers have rushed to join civil society monitoring groups.

Oy ve Otesi ("Vote and Beyond") is one such initiative. Founded in response to 2013's Gezi Park protests, its members observed local elections last year and the presidential poll that saw Erdogan take office.

"The reason we started this is that there was a lot of talk about rigging on election days, and our entire generation read news and columns around the topic. We decided enough was enough and that the only way around it was an independent, unbiased organization," co-founder Sercan Celebi, 32, told VICE News.

The group monitors the voting process as well as the counting and subsequent aggregation of votes. Its members are trained to legally intervene on the spot if they witness malpractice, rather than just reporting it after the fact, says Celebi, the former CEO of a social media company.

On Sunday, the organization's team of more than 60,000 volunteers hopes to cover around 100,000 of the country's 140,000 polling stations in 45 of 81 provinces. Celebi expects the atmosphere to be tense, especially following Friday's bombing at an HDP rally that killed two and injured more than 200. "In this particular election, people are very polarized. With the bombings just yesterday, it will be, to say to the least, not a comfortable election," he said.

Turkey's electoral history has been seen as broadly legitimate, but last year's polls were marred by allegations of irregularities and vote rigging on an unprecedented scale. The Supreme Electoral Board (YSK), which oversees Turkish elections, ordered only two reruns despite 1,400 allegations of irregularities, mostly from opposition parties, according to the Bipartisan Policy Center.

This time around, the YSK has also rejected complaints made by opposition groups against Erdogan, who has ignored the presidency's mandated neutrality to party politics and campaigned relentlessly for the AKP. Kemal Kirisci, director of Brookings' Turkey Project, told VICE News the cajoling by the president was a "pretty much blatant violation of the constitution."

The president has also continued to tighten control of the police, judiciary, and media. Journalists have been prosecuted for critical coverage, and even for insulting Erdogan on Facebook or Twitter.

Against this background, fears of misconduct are justified, says Steven Cook, Hasib J. Sabbagh Senior Fellow for Middle Eastern Studies with the Council on Foreign Relations. "The concerns over the integrity of the ballot box are not misplaced," Cook told VICE News. "Although Turkey doesn't have a history of electoral fraud, there were serious allegations that the AKP fixed the 2014 Ankara mayoral election. The charges of fraud were swept under the rug."

Nevertheless, Celebi insists that Oy ve Otesi is not a partisan organization. He says they have sat down with representatives from all of the political factions, and that they remain dedicated to fair, accurate polls, rather than combating Erdogan or the AKP. "We're primarily interested in the process, not the results of the elections," he says.