Liberal politicians across Europe should remind voters that patriotism is not at odds with pride in the European Union if they want to win at the polls, the Austrian president-elect’s campaign manager has said.

The advice on how to fight Eurosceptic populism came a day after Alexander Van der Bellen, a Green-backed independent, decisively beat his rightwing populist rival, Norbert Hofer, in a rerun of the Austrian presidential election.

Martin Radjaby, managing director of the agency Jung von Matt, which coordinated the winning campaign, told the Guardian: “Van der Bellen’s success in Sunday’s election has shown that liberals can reclaim subjects currently occupied by populists and nationalists, such as tradition and patriotism.”

On Sunday, Van der Bellen managed to increase his majority from around 30,000 to almost 300,000 votes, dealing a crushing blow to his opponent from the anti-immigration Freedom party (FPÖ). The 72-year-old retired economist had run a campaign which gave equal weight to a message of pan-European cooperation and the notion of Heimat, meaning “homeland” or “spiritual home” in a broader sense.

One poster showed Van der Bellen against the backdrop of his home town in the Tyrolean Alps, along with the slogan: “Wer unsere Heimat liebt, spaltet sie nicht” (“Those who love their homeland do not divide it”).

Radjaby said that far from emboldening Austria’s rightwing populists, Britain’s vote to leave the European Union and Donald Trump’s win in the US election had played into his team’s hands. “Brexit intensified the debate about Europe and allowed our candidate to become a unifying figure,” he said.

After the country’s constitutional court in July annulled the narrow outcome of the run-off due to irregularities in the count of the vote, Van der Bellen’s team started using the colours of the Austrian flag on its posters, while simultaneously warning that a vote for his rightwing rival could lead to Austria leaving the EU.

While the former leader of the Green party drew his best results in urban areas, he managed to increase his share of support in rural parts of the country such as Vorarlberg in the westernmost tip of Austria, where he got 60.4% of the vote.

Even though the centre-right ÖVP had not officially endorsed Van der Bellen, he managed to win the support of many of the party’s regional mayors, who in Austria are elected via a direct mandate. Compared with May, Van der Bellen gained 144,000 net votes from previous non-voters.

Many of those who swung to Van der Bellen were female, a trend some commentators put down to an inclusive viral video campaign featuring female protagonists such as “Gertrude”, an 89-year-old Holocaust survivor from Vienna. Sixty-two percent of Austrian women voted for Van der Bellen, up from 54% in May.

According to Reinhard Heinisch, professor of political science at Salzburg University, Van der Bellen’s authentic, unconventional appearance played a key part in swinging the vote. Heinisch said: “He’s not a career politician and didn’t come across as one. He stayed true to his unpolished self. Sunday’s vote has shown us that while there is potential for a protest vote, it doesn’t always have to go to the far right. There is such a thing as a radical centre.”

Matthias Strolz, leader of Austria’s liberal NEOS party, said: “Brexit was definitely a crucial issue for the outcome of the election.” Nigel Farage, the former leader of Ukip, told America’s Fox News on Friday that Hofer “will be calling for Austria to have a referendum on their membership with the European Union”. Strolz said the comments were “a great goal for Van der Bellen”.

“Ten years ago we used to say that the last week of an election doesn’t matter, but in the days of social media that is different. I saw how it shook people up,” Strolz said.

“There’s an encouraging lesson in Sunday’s result: even in a country with a history of strongly Eurosceptic attitudes such as Austria, a politician can campaign around the idea of a united states of Europe and still win an election.”

Christoph Hofinger, co-director of social research company SORA, told Der Standard newspaper that Trump’s success in America may have inspired Hofer to go for a more aggressive tone in the last round of TV debates. “In a democracy where three-quarters of eligible voters actually turn out at the voting booth, that is more risky than in the US, where brisk behaviour can mobilise your core support,” he said.

Hofer’s party tried to project optimism on Monday, with its leader, Heinz-Christian Strache, writing in a Facebook post: “2017 will be the year of the Freedom party! Our time will come!”

The FPÖ is currently leading polls for the next parliamentary election, which could take place next year if the current coalition government between centre-left and centre-right collapses. Given Hofer’s strong showing in the presidential election, Austrian media have speculated that the failed presidential challenger could replace Strache at the top of the far-right party, which governed in a coalition with the conservatives between 2000 and 2005.

Hofer on Sunday evening denied that he would challenge Strache for the party leadership, saying that he was planning to run for the presidency again in 2022.