Hungary's Viktor Orban, Europe's hard-liner on immigration, on Friday hailed his common eurosceptic path with Poland's right-wing government as he headed into an election which seems certain to hand him a third straight term in power.

After a campaign in which Orban has positioned himself as a saviour of Hungary's Christian values and culture against a flood of Muslim migrants, all opinion polls put his Fidesz party well in the lead for Sunday's election.

An emphatic victory could embolden Orban, Hungary's longest serving post-communist prime minister, to solidify a Central European alliance against the European Union's migration policies, and against a deeper integration of the bloc which he opposes.

It would also give a boost to other rightwing nationalists in Central Europe, in Poland and in neighbouring Austria, and expose cracks in the EU bloc.

On Friday he voiced common cause with Poland, whose governing Law and Justice (PiS) party like Fidesz is under fire from the European Union over their refusal to take in migrants under a quota system and over their efforts to tighten state control of their courts and media.

"We believe Poles and Hungarians have a common path, common fight and common goal: to build and defend our homeland in the form that we want ... Christian and with national values," Orban said on at the unveiling of a statue marking a 2010 plane crash that killed the Polish president.

Poland could count on Hungary in its brushes with Brussels because "when Poland is attacked then it is Central Europe under attack," he said.

Poland's PiS leader, Jaroslaw Kaczynski, attending the ceremony commemorating the plane crash in Russia in which his twin brother was killed, endorsed Orban ahead of Sunday's vote.

"The dignity and freedom of nations is closely linked to Viktor Orban's name not just for Hungarians, but for Poles as well," Kaczynski said through an interpreter.

Orban's Fidesz party, with a firm grip on the media, dominates the public agenda. All polls predict a win for him on Sunday though something short of the landslides of the 2010 and 2014 elections.

There is also a slight chance that the fragmented opposition, with former far-right Jobbik as the main challenger, could upset a smooth victory and strip Fidesz of its parliament majority.

Orban, 54, who started out as a young liberal activist in the late 1980s, has transformed Hungary's democratic fabric in the past eight years with what his critics see as an increasingly authoritarian style.

His government has expanded control over the state media, and via business allies, also large chunks of the private media.

Businessmen close to Fidesz and Orban have acquired stakes in major industries like banking, energy, construction, and tourism, enriching themselves on EU funds.

In clashes with Brussels over his policies, he has ruled out taking part in any EU-wide mechanism to settle migrants from the Middle East in Hungary, saying the Christian country, which has no history of large-scale immigration, should preserve its "ethnic homogeneity."

"Brussels ... wants to dilute the population of Europe and to replace it, to cast aside our culture, our way of life," he said in a speech on March 15.

In 2015, even before the peak of the migration crisis, Orban realised that the threat from what he called "an invasion" by Muslim immigrants struck a chord with a large part of the Hungarian electorate.

His government built a fence on the southern border with Serbia to keep out migrants, when hundreds of thousands walked though Hungary on their way to richer western Europe.

The pre-election campaign has vilified U.S. financier George Soros whose philanthropy aims to bolster liberal and open-border values in eastern Europe, and runs against Orban's concept of an "illiberal democracy".

The fierce anti-immigrant campaign has gone down well with around 2 million core voters of Fidesz. According to a poll and estimates by Republikon institute on Thursday Fidesz could win 113 seats in Hungary's 199-seat parliament.

However, the polls could be unreliable as one-third of voters are uncertain and many hide their voting preference.

Sitting on a bench in Budapest, enjoying the sun with a cup of coffee in his hand, Istvan Nagy, a 50-year old plumber says he will vote for Orban whom he sees as a guarantor of security.

"Of course, Fidesz, Viktor Orban! Why? Because he is the only one who makes me feel secure in this country, this is what I have got used to and I want this to remain," he said.]

"We have a job, and money and also the girls are pretty here."

While Orban has gradually become a nationalist admired by far-right politicians across Europe, he is credited with keeping the budget deficit under control, reducing unemployment, and cutting some of Hungary's debt pile.

His income tax cuts have put the economy on a growth track, with the economy expanding by 4 percent in 2017 and consumption and lending on the rise.

Financial markets have been pricing in a new term for Orban, and have mostly cast aside the chances of a Fidesz defeat.

That could trigger a fall in the forint and government bonds in the event of an upset, traders say.