Fidesz party lawmakers made the commitment at a congress of the European People's Party group, where an "emergency resolution" was introduced partly to establish where the stridently nationalist party's sympathies lay.
Delegates at the congress vowed to promote the values of "human dignity, freedom, democracy, equality, the rule of law and respect for human rights." democracy, equality, the rule of law and respect for human rights."
The EPP, the group uniting Europe's center-right parties, has been wringing its hands over whether to keep Hungarian Prime Minister Viktor Orban and Fidesz in the fold or cut them loose before European Parliament elections in May.
Far-right and populist parties have made big gains in EU countries as their leaders bicker over what experts say should be an eminently manageable level of mass migration. Orban's government erected razor-wire fences to keep migrants out as hundreds of thousands of people — most of them refugees from Syria and Iraq — tried to enter Europe in 2015.
EU lawmakers voted in September to pursue unprecedented action against the Hungarian government for attempting to undermine the bloc's democratic values and rule of law. However, some EPP insiders fear that pushing Orban out might push him into the arms of far-right parties such as nationalist Alternative for Germany (AfD) or France's National Rally.
Others worry that a policy of containment might undermine the EPP and shift it further right. A recent battle between Brussels and Italy's populist government over the country's budget plans and stalled negotiations over Britain's departure from the EU in March are other sources of concern that the European project could face chaos after the May parliamentary polls.
In their resolution in Helsinki, Finland, delegates underlined that the group's values were "being challenged in an unprecedented manner" and said populist and nationalist extremism were among the biggest threats "to freedom and democracy in Europe since the fall of the Iron Curtain."
The two-day meeting — involving government leaders from Germany, Austria, Bulgaria, Croatia, Hungary, Ireland, Slovenia and the EU's main institutions — is a chance for the group to thrash out its strategy to hold power in the polls and nominate its lead candidate.
Two men are in the running for that role and vying to become the next president of the European Commission, the powerful executive arm that proposes and enforces EU laws. The favorite is Germany's Manfred Weber, a 46-year-old conservative's conservative from Bavaria. Weber is more open to accommodating Orban and has received the Hungarian leader's endorsement in the runoff.
His opponent, Alexander Stubb, is a former Finnish prime minister and part-time triathlete with a slick social media campaign that promotes him as part of "the next generation of Europe." Ahead of the resolution vote, Stubb told The Associated Press that if Orban "signs it, he continues in the party but sticks to the line and stops talking about illiberal democracy, which is nonsense." He added: "If he doesn't sign it, he's out."
Asked by AP why the EPP even felt it had to define its values in a resolution, Weber said "there is no debate about any kind of value inside the EPP group." He said the EPP "invented" the European dream.
Austrian Chancellor Sebastian Kurz, whose governing coalition includes a far-right party, said that "the cores values that we have in Europe are sacred, and they should be protected in member states."
EPP patriarch, group President Joseph Daul, played down the concerns about Orban. "In every family there is an enfant terrible," Daul said. "But because I'm a Christian Democrat, I prefer to keep my enfant terrible inside the family and to be able to talk to him and reason with him."
The EPP's main opposition, the Socialists and Democrats, will have current Commission Vice-President Frans Timmermans standing as their lead candidate, and the center-left is already accusing its rivals of selling out.
"Conservatives are clearly no longer reliable partners when it comes to fighting the dark forces that are trying to undermine rule of law, democracy and solidarity in Europe," Socialist leader Udo Bullmann said in a statement Wednesday.
David Keyton and Jari Tanner contributed to this report.