In the run-up to the EU referendum in 2016, about 650 people attended a Nigel Farage Ukip rally at the Neon venue in Newport, south Wales, which was judged a roaring success.

When Farage’s Brexit party launched its campaign for the European elections at the same venue, more than three times that number packed in to cheer, clap and holler.

“It was electric,” said the Brexit party’s lead candidate in Wales, Nathan Gill. “We’ve seen nothing like it.” Gill claims those present were not merely the same old faces who had supported Ukip and switched allegiance. “There were brand new people there, motivated to come out and support us,” he said.

There are four European parliament seats up for grabs in Wales. In 2014, Labour, Ukip, the Conservatives and Plaid Cymru won one each. This time, there is a chance the Brexit party may win two.

“You have to remember that Wales voted to leave,” said Gill, who was elected for Ukip five years ago. “A lot of people forget how Brexiteer Wales is.”

The Brexit party claims it is attracting voters from across the political spectrum. Gill said he had recently been approached by someone in the McDonald’s in Merthyr Tydfil, a Labour heartland.

“He said: ‘Do you know what really annoys me? They keep telling me I was thick and didn’t know what I voted for. Of course I knew what I was voting for’,” Gill said.

Over the weekend, Gill was in the seaside resort of Llandudno in north Wales. “Senior members of the Conservative party were coming up to me telling me everyone was voting for us. They are so furious with what their party is doing,” he said.

Labour has won all but one of all Wales-wide elections since 1918, but many supporters fear it will be beaten this month by Farage’s party.

While Gill was chatting to Tories in Llandudno, one of Labour’s candidates, Matthew Dorrance, the group leader on Powys county council, was knocking on doors in the Cardiff North constituency.

He said “It’s all positive” but did not want to discuss the issues that were being raised, instead asking for questions in writing so they could be seen by the Labour press office.

Such sensitivity is not surprising. Labour in Wales is accused of being in a muddle over whether to back a “people’s vote”. Its four European parliamentary candidates have clearly said they are in favour, but many voters in the party’s heartlands, such as Merthyr, voted to leave.

The European elections are the first real test for Labour’s new leader, Mark Drakeford, who has been first minister since December. Roger Awan-Scully, the head of politics and international relations at Cardiff University, said bad results for Labour would make Drakeford – perhaps unfairly – look like a loser.

Awan-Scully lives in Cardiff North, a bellwether constituency, and is usually deluged with leaflets and canvassers. Not this time. “All I’ve seen is a Brexit party leaflet,” he said.

Nevertheless, Awan-Scully said it would be a huge shock if Labour did not win one seat. If the Brexit party wins two, it may be the Tories that lose out.

The election is also a test for another new leader, Plaid Cymru’s Adam Price, whose weekend included addressing a lively independence rally attended by thousands. Price is calling for a referendum on independence if there is no further vote on Brexit.

He admitted Plaid, like all parties in Wales, had struggled to get itself ready for an election it had not planned for.

But he said he had been surprised at how open people were to having serious conversations on the doorstep. “People are engaged, interested,” Price said. “Young people especially are galvanised like never before in recent years.”