WARSAW (Reuters) -The candidates still in the running to become Poland's president were given lists of demands from two far-right politicians supported by more than a fifth of voters on Tuesday, as they compete to broaden their appeal.

Centrist front-runner Rafal Trzaskowski and his nationalist opponent Karol Nawrocki would need to gain a chunk of the votes that went to far-right candidates to have a chance of victory in a June 1 run-off. But the behaviour of these mainly young and anti-establishment voters is hard to predict.

In particular Trzaskowski, from the ruling Civic Coalition (KO), could face a tricky balancing act as he tries to reach out to people who backed far-right Confederation party leader Slawomir Mentzen without alienating left-wing or centrist voters.

In a recorded message, Mentzen, who finished third in the first round with 14.8%, said on Tuesday that he would invite Trzaskowski and Nawrocki to take part in a debate on his YouTube channel.

"During the conversation, I will ask you to sign a declaration in line with the expectations of my voters," he said.

The declaration included promises not to raise taxes, not to limit freedom of speech, not to send Polish troops to Ukraine, not to transfer powers to the European Union, and not to limit Poles' ability to carry weapons.

Asked about Mentzen's invitation to a debate, Nawrocki, who is backed by opposition party Law and Justice (PiS), told a news conference that it was "a serious offer from a candidate who wants to talk about the future of Poland before giving his support", adding he should talk to Mentzen about an endorsement.

Trzaskowski told reporters he had not yet made a decision on taking part in the debate.

Meanwhile Grzegorz Braun, who in 2023 used a fire extinguisher to put out Hanukkah candles in the country's parliament, an incident that caused international outrage, published a list of questions for Trzaskowski and Nawrocki.

These included whether they would stop the "Ukrainisation" of Poland - a reference to the hundreds of thousands of refugees from the neighbouring country - reject the EU's migration pact and Green Deal climate-change policies, oppose abortion and cease Hanukkah celebrations in the Presidential Palace.

Braun finished fourth in the first round with 6.3%.

(Reporting by Alan Charlish, Pawel FlorkiewiczEditing by Peter Graff)