Yet Ms Machado, who counts Margaret Thatcher as one of her political heroes, is not even a candidate in the presidential race.

After winning more than 90 per cent of the votes in the UDP’s primary last year, she was barred from public office by a Chavista-packed court for supposed corruption and supporting US sanctions against the dictatorship.

She promptly threw her support behind a back-up candidate, Edmundo González, 74, a little-known, softly spoken retired diplomat and amateur birdwatcher.

The pair often campaign together now, braving police roadblocks and government harassment as they travel by car because of a ban on Ms Machado flying.

Hotels where the pair have stayed and restaurants where they have eaten have often been shuttered by the regime, prompting the pair to rely on the hospitality of local supporters.

Should the opposition win, Ms Machado is widely expected to be the de facto leader of a government formally led by Mr González.

Polls show him on more than double the level of support for Mr Maduro. The remainder of the vote is shared by around a dozen smaller candidates widely viewed as stooges of the regime.

‘It’s hard to imagine they will hand over the keys’

“I’m sure they [Ms Machado and Mr González] represent change, for a prosperous Venezuela, where there’s no persecution and those of us who see things differently to the government can be adversaries, not enemies,” Milagros Gómez, a retired lawyer who attended a rally held by the pair at the Central University of Venezuela in Caracas last Sunday, told The Telegraph.

But for that to happen, Mr Maduro must be prepared to relinquish power, something that strikes Michael Shifter, a Latin America expert at the InterAmerican Dialogue, a Washington DC think tank, as “pretty far-fetched.”

“It’s hard to imagine that without guarantees for Maduro and those in his inner circle, and all the accusations, including of crimes against humanity, that they are just going to hand over the keys and walk away,” he says.

Nevertheless, even with electoral fraud, this month’s vote and the opposition’s new-found unity could signal the start of a long, painful democratic transition, Mr Shifter believes: “There will be significant actors within ‘Chavismo’ who will see the writing on the wall.”

But for that to happen, citizens will need to make their weight felt and vote in significant numbers next Sunday, even if the Maduro government ultimately manages to fake, at least temporarily, an improbable electoral comeback.