A political newcomer who is causing headaches for Hungary’s government has said his experience as a regime insider can help him succeed where other opposition figures have failed, citing his “crazy” rise in the polls and “vision” as signs that change is possible. Fourteen years after the Hungarian prime minister, Viktor Orbán, returned to power and put the country on an illiberal path, some Hungarians had lost hope that his hold on power could be eroded. But Péter Magyar, a former member of the ruling Fidesz party’s most elite circle, is now on a mission to convince Hungarians that Orbán’s government should – and can – be defeated. “Two months ago, nobody knew me in Hungary,” Magyar said in an interview with the Guardian. “Today, we had the biggest political rally.” It was 9pm on Saturday night, and Magyar was sitting at a coffee shop near Hungary’s parliament with a glass of Coca-Cola, at the end of a marathon day that, he hopes, could mark a turning point for Hungary. Hours earlier, he led a demonstration of tens of thousands in front of the parliament building. The protesters sang together and held hands, as Magyar urged them to put ideological differences aside and unite to create a different future for the country. But even after the vast crowd headed home, some stayed behind, excitedly waiting for a selfie with Magyar, who has become a household name in recent weeks. The 43-year-old garnered national attention after openly breaking with the government, going to prosecutors with allegations of corruption, and making public a recording of Judit Varga, his former wife, who used to be the country’s justice minister, discussing what Magyar has described as corruption at the highest levels of government. He has differentiated himself from Hungary’s struggling opposition parties by criticising not only Orbán but also some of the government’s opponents, and asking conservative, leftwing and liberal Hungarians to join his movement. “The aim, of course, is to have a party, to be able to run for the European parliament elections on 9 June,” Magyar said, estimating his support at about 15% to 21%. “It’s crazy,” he said. “I will be on the top of the list,” he said. But added: “My intention is not to go to Brussels, because I have to build the party in Hungary.” Asked what sets him apart from other Hungarian opposition political figures who tried and failed to appeal to a broad segment of voters, Magyar – who has relied heavily on social media to build his new political brand – stressed his experience within Orbán’s system. “I am new, a newcomer – but I am not new, because I’m very experienced,” he said, pointing to his years of working as a Hungarian diplomat in Brussels, his past membership of the Fidesz party, his connections to decision-makers and his involvement with Varga’s social media communication. And, he emphasised: “I have a vision about Hungary.” Government officials have sought to downplay Magyar’s importance, and have repeatedly denied his allegations of corruption. But the new opposition movement has visibly shaken the ruling party, with government-controlled outlets sometimes running dozens of articles attacking his project and character each day. The coverage has focused in part on recent claims from Varga that he mistreated her during their marriage. Magyar, who has shared residence arrangements with Varga for their three children, has denied the allegations, saying they are part of a “propaganda campaign”. Nevertheless, some opposition politicians and supporters have expressed scepticism about Magyar and his strategy, as well as fears that he could dilute the already-divided opposition vote. Asked about these concerns, Magyar said: “It’s not my problem, I think,” noting that he believeed 30% of his support came from opposition voters, 30% from independents and 20% from government supporters. Speaking of his efforts to upend the traditional political landscape, he pointed to the example of Emmanuel Macron, the French president, who left the Socialist party and created a centrist movement. “This is my aim, to be in the centre,” Magyar said, adding that he had things in common with both Orbán and the opposition. Magyar’s messaging has focused heavily on domestic issues, in particular fighting corruption and improving Hungarians’ quality of life. In the interview, he criticised Brussels but also stressed the need for a constructive relationship with the EU. “I can tell you that I’m a bit closer to the position of Fidesz than the opposition, but what’s for sure is that we are a member of the club and we should behave like a member of the club,” he said. The EU’s policy towards Orbán has helped the ruling party, Magyar argued. “I’m not a big fan of this federal European superstate, so I believe in strong member states and a strong EU,” he said. But Magyar also said he would end Hungary’s rule-of-law conflicts with the bloc. “We can have debates, but you should be constructive,” he said.