BRUSSELS — As Italy’s new populist leaders prepare to form a government, European leaders are bracing for potential new confrontations over migration and some of the core principles of the common currency, the euro.

They were already trying to tame a rebellion against Europe’s shared democratic values in the east, led by Hungary and Poland. They now face the prospect that Italy, a founding member and Europe’s fourth-largest economy, could be next to challenge the bloc’s cohesion, finances and democratic principles.

If nothing else, anxiety about the economic plans of the new Italian government may finish off the ambitious reform agenda for a more integrated euro area proposed by the French president, Emmanuel Macron.

“The new Italian government will give Germany every excuse not to do what Macron would like and it will destabilize the markets,” said Charles Grant, director of the Center for European Reform, a research institution. “It will increase the risk of another eurozone banking crisis, not reduce it.”