On Sunday, Orban's plan will be put to a stern test in a national election where polls suggest six opposition parties united against him for the first time are within a striking distance from unseating his nationalist Fidesz party.

Fidesz swept elections in 2018 on a fierce anti-immigration campaign that earned him praise from former U.S. President Donald Trump and Europe's far right and set him on a collision course with Brussels.

Now, the 58-year-old leader, who has transformed Hungary into a self-styled "illiberal democracy" with a firm grip over media and loyalists in charge of top institutions, acknowledges this election will not be a walkover.

"The stakes of this election are, even for an old warhorse such as myself, much higher than I could have ever imagined," Orban, who has evenly split the time in opposition and in power since post-communist Hungary's first election in 1990, told pro-government channel HirTV on Monday.

Opinion polls give Orban's party a narrow lead, but with about one-fifth of Hungary's 8 million voters still declaring to be undecided, the April 3 vote could still go either way.

The vote will decide whether Brussels will continue to face resistance from Hungary and Poland over media freedoms, rule of law and minority rights or Warsaw will be left isolated in its standoff with European institutions.

Defence of conservative Christian family values against what he calls "gender madness" now sweeping Western Europe is part of Orban's current campaign. On Sunday, Hungarians will also vote in a government referendum about sexual orientation workshops in schools, a vote which rights groups have condemned saying it fuelled prejudice against the LGBTQ community.

EAST OR WEST?

Hungarian Prime Minister Viktor Orban leaves the stage after delivering his annual state of the nation speech in Budapest, Hungary, February 10, 2019.

Russia's invasion of Ukraine upset Orban's script, casting his close relations with Moscow in a new light.

He responded by tapping into Hungarians wish for security, posing on campaign billboards as their protector and accusing opposition politicians of trying to drag Hungary into the war, a charge they have denied.

Yet the opposition leader Peter Marki-Zay seized the opportunity, telling voters they faced a choice between the West and East, criticising Orban's close relations with Russia and what he said was an erosion of democratic rights.

Campaigning in what used to be called Moscow square in Budapest, an opposition stronghold, Marki-Zay said on Tuesday that Russian President Vladimir Putin was rebuilding the Soviet empire and Orban "still cannot decide how to keep an equal distance from the killers and the victims."

Addressing cheering supporters, the conservative small-town mayor and a Catholic father of seven, brought up the Hungarian uprising crushed by Soviet tanks almost 66 years ago while taking a swipe at Orban.

"After 1956 there is still a Hungarian politician, who cannot state that we always must stand up against the aggressor," he said.

Marki-Zay leads a coalition of six parties across Hungary's political spectrum that joined forces, galvanized by the possibility of ousting Orban.

Its members, from leftist Democratic Coalition, to liberal Momentum and Jobbik, a far-right party turned moderate, have put most of their disputes aside for the campaign but policy differences may pose a challenge if Marki-Zay wins on Sunday.

He has promised to clamp down on corruption, gain access to European Union funds frozen by Brussels over the rule of law fight, and introduce the euro.

"What will decide this election is that the majority has had enough of these 12 years," said Sandor Laszlo, who attended Marki-Zay's rally in the capital.

According to the latest poll by Zavecz Research, Fidesz led the opposition by three percentage points with 39% support. Tibor Zavecz, director of the think tank, said Fidesz appeared to have a better chance to win but a lot would depend on a last-minute mobilisation of voters.

He said around 8% of the electorate, around 600,000 people, said they would cast a vote but still had no preferred choice.