When Matteo Salvini last visited the Italian coastal town of Pesaro for a rally before regional elections in May 2015, he was pelted with eggs and tomatoes. Ester Principi, who was standing close to the stage on Piazza del Popolo, found herself in the line of fire. “They managed to splatter me, too,” she said.

Four years on, much has changed. This time Principi reclaimed her front-row position on the same square as she waited on a damp May morning for the man now affectionately called the “captain” by his loyal supporters.

“He wasn’t well-liked before, but many people here love him now,” she said. “He represents the people, and defends us.”

A fortnight before European elections that have been cast as a battle for the continent’s soul between a pro-European mainstream and resurgent far-right, populist and EU-critical parties, including Salvini’s League, the powerful Italian interior minister had taken his campaign to the central Marche region, a resolutely leftwing stronghold since the end of the second world war.

He found an eager audience. Principi’s friend, Antonio Alfieri, a recent defector from the Democratic party, which was removed from power last June by Salvini’s far-right League and the anti-establishment Five Star Movement (M5S), said the centre-left party “no longer considers Italians. They have moved too far away from the people.”

Salvini kept the crowd of several hundred in Pesaro, birthplace of the great composer Rossini, waiting in the rain before leaping onto the stage, clad in a blue, zipped sweatshirt with “Italia” written across it and Nessun Dorma, the powerful Puccini aria that regularly features at his rallies, playing in the background.

Promising to reopen hospitals, crack down on drug dealers and prioritise Italians over immigrants for social housing and other benefits if the League ousted the left after communal elections also due on the same day, he pledged to defend the region’s agricultural workers and fishermen, “who have been massacred by European regulations”.

There were pockets of resistance. A group of around 15 interrupted the speech, shouting: “We hate the League! Fascist! Liar!” Rosanna Ardone, a staunch leftwing voter, said she loathed Italy’s most powerful politician. “He does all these selfies to give the impression that he is loved, but in reality he is a fake,” she said.

The main problem for Salvini dissidents, though, is that they feel they no longer have a party to turn to, whether locally or at the European level. The Democratic party is not “the real left”, they say, and M5S too ambivalent. “When fascists rise, it’s because the left is weak,” said Alessandro Admiri, one of the protesters.

Many, though, had plainly decided to take the plunge. Aravena Vollí, another Democratic party defector, said she had not wanted to switch parties, but the left had simply “failed to provide essentials, such as jobs. They don’t help the weaker people or ordinary workers – they help bankers and stronger classes.”

An ebullient Salvini mocked his protesters and defended the League from accusations of racism and fascism: “If the left is resorting to fascism when there is no fascism, and racism when there is no racism, then they are finished,” he said. “We are only fighting for Italians who are proud to be Italian.”

Unlike in the UK, most of Europe's populists no longer want to take their respective countries out of the EU

It is a message that is being heard not just in Italy but across the continent. In a European election poll last week, the League held a commanding lead with 30.9%, compared with just 6.4% in the previous 2014 elections, with M5S on 24.9% and the centre-left Democratic party on 20.5%.

In Britain, an Opinium poll for today’s Observer, looking at European election voting intentions, puts Nigel Farage’s Brexit party on 34 points, 23 points ahead of the Tories and 13 ahead of Labour.

Elsewhere in Europe, polls suggest EU-critical parties could become the second-largest force in the parliament, with up to 35% of its 751 seats. Representatives of three of them – Germany’s Alternative für Deutschland (AfD), the Danish People’s party and the nationalist Finns party - joined Salvini, who is also Italy’s deputy prime minister, on stage in Milan last month to launch the European Alliance for People and Nations, an alliance of nation-first, anti-immigration parties that also includes Marine Le Pen’s National Rally (RN) from France and up to five others.

Observers say it remains doubtful if Europe’s myriad sovereignist and EU-critical parties, who share the same broad goals of returning power to member states and further curbing immigration, but often have radically different economic and social policies, as well as diametrically opposing views on Russia, can succeed in forming and maintaining a coherent group.

Nor is it yet clear which parliamentary groups two of Europe’s strongest nationalist parties – Poland’s ruling authoritarian Law and Justice (PiS) party, part of the rightwing European Conservatives and Reformists bloc, and Hungarian prime minister Viktor Orbán’s illiberal Fidesz, currently suspended from the centre-right European People’s party (EPP) - will decide to join.

Unlike in the UK, most of Europe’s populists no longer want to take their respective countries out of the EU – the chaos of Brexit has seen to that. In 2016 at least 15 parties were campaigning for a referendum on EU membership; today, faced with 30-year-high approval ratings for the EU across the bloc, they instead want a different kind of EU, focused more on security, immigration and “nation first” economics.

But in a newly fragmented parliament, with both the EPP and the centre-left Socialists and Democrats (S&D) group set to lose significant numbers of seats and their long-dominant “grand coalition” on course to fall short of a parliamentary majority for the first time, the potential for EU critics to shape the bloc’s future is plain.

No longer a mere talking shop, the European parliament now has significant powers in the EU law-making process: the European commission proposes directives and regulations, but it is MEPs and the council of ministers – government members from all 28 countries – who amend and approve or reject them.

In the new parliament “the centre-right and centre-left coalitions that pass legislation will be smaller, and majorities more difficult to form,” said Simon Hix, a political scientist at the LSE. “As a result, populist, EU-critical MEPs will be able to shape the policy agenda. They’re also likely to win key policy-making positions in parliament, such as committee chairs.”

Until recently the self-appointed standard-bearer for the pro-European cause was Angela Merkel

This new influence, Hix said in a report for the academic thinktank UK in a Changing Europe, means they are likely to demand “more restrictive refugee and asylum policies, more spending on EU external border controls, more powers for national governments to run eurozone budget deficits, and more protectionist trade policies”.

The struggle between those pursuing a “Europe of nations” and those who believe in a more integrated, open Europe is being played out across the continent. In Poland a normally divided opposition has formed a broad alliance that is currently polling a close second to the nationalist, arch-conservative PiS.

Founded in February, the European Coalition of Opposition Forces – made up of the Civic Platform, formerly led by the European council president, Donald Tusk, and a collection of leftwing and rural politicians – has emerged as the first potential challenge to PiS, with the European vote shaping up as a test before national elections due in the autumn.

“If we manage to win, it will be a signal to all countries in Europe,” said Civic Platform’s leader, Grzegorz Schetyna. “This election, in Poland, will show that you can successfully combat populism, you can effectively combat those who demolish democracy.”

With the German chancellor, Angela Merkel, expected to stand down by 2021, and her successor as leader of the Christian Democratic Union, Annegret Kramp-Karrenbauer, lacking her clout in the international arena, the role of pro-European standard-bearer has been taken up by France’s young centrist president, Emmanuel Macron.

Elected in 2017 on a passionately pro-EU platform, Macron has described the 2019 elections as “decisive for the future of our continent” at a time when Europe “has never been in so much danger”.

If Macron is seen as a one-man buffer against European populism, then the northern French city of Amiens is a bulwark within that buffer. It is where Macron was born and grew up. His wife Brigitte is from there, too; the sixth generation of her family currently runs its most famous chocolate shop.

The city, 75 miles north of Paris, is the capital of the Somme, a department that voted 37.15% for the Front National – now the RN – in the last European elections in 2014. Few of those ballots, however, were cast in Amiens.

'The problem is out in the rural areas, the villages where people feel far from where the decisions are being made'

The city’s deputy mayor, Jean-Christophe Loric, local president of the liberal MoDem party, which has allied with Macron’s La République en Marche (LREM) for the elections, said Amiens had often bucked the extremist trend in northern France. “In the 2015 regional elections the FN gained 40%, but only 15-16% in Amiens,” he said. “Because we have invested in people’s lives massively here. People here are not afraid of foreigners or different cultures. The problem is not in the towns and cities, it’s in rural areas where people are more afraid of Europe; they fear losing their jobs and public services and transport and schools and they feel excluded.”

Bruno Bienaimé, LREM’s representative in the département, agreed. The far right had little support in town, he said: “The problem is out in the rural areas, the small villages where people feel far from where the decisions are being made.” Convincing those in rural areas to shun Marine Le Pen and the far right while canvassing door-to-door in rural areas, he admitted, was “more complicated”.

Thirty-four different parties are taking part in the elections in France, with several recent polls suggesting Le Pen’s National Rally list, headed by 23-year-old Jordan Bardella, may be edging ahead of the Renaissance list made up of centrist candidates from various movements and parties led by former LREM Europe minister Nathalie Loiseau.

Renaissance’s 79-proposition manifesto, published on Thursday, promised to “take our European destiny in hand” and led with a proposal for a European climate bank with €1,000bn in funds to finance an EU-wide ecological transition. The RN’s 76-page manifesto was an anti-federalist tract promising to “Save Europe from the EU”.

In the centre of Amiens it was hard to find far-right supporters, even among the politically disillusioned. Catherine Bourbon, 26, a hospital casualty doctor, said she was disappointed with all political parties, but would never vote for the RN. “It’s the same old disappointments, whoever the party or the person. I was so disappointed with all of them when I started working in the hospital and saw the politics in action. The FN/RN try to envelop people with their promises of change, but its just racism and xenophobia. They’re trying to make themselves seem nicer, but they’re not,” she said.

'I don't underestimate the threat, or the populists' capability to lie to get votes'

Like many French voters, Lucie Jacquet, 28, a mathematics professor, said she was “very pro-Europe”, but was fed up with being railroaded into voting for Macron just to block the far right. “The problem with voting for the party in power to stop Le Pen is that it gives them (LREM) the idea they are supported, when it is actually a vote against the RN,” she said, adding: “It’s complicated because I’m absolutely against the politics of the RN and Marine Le Pen.”

Outside Amiens’s magnificent cathedral, Dominique Bernard, 61, a headmaster, said he was a lifelong Europhile. “Europe and its principles of fraternity are the only progressive path for humanity,” he said.

“I was born in 1958 and was lucky to share time with my grandparents and family who lived through the wars. I am persuaded that Europe is one of the best ramparts against the forces of division which could lead to another conflict on European soil.”

Loric, Amiens’s deputy mayor, said he was “optimistic” for the vote’s outcome in his region; his campaign has been helped by a €100m loan from the European Investment Bank to revamp many of the city’s council homes.

“I don’t underestimate the threat, or the populists’ capability to lie to get votes. But we are doing things here for people with the help of Europe, and people are not stupid – they vote for those who invest in them, their town, their futures,” he said. How far that view prevails will become clear very soon.