The cynical reading is that Ms. Merkel has stayed tough out of concern for her re-election chances in September’s parliamentary elections. “The rescue package for Cyprus is written in the handwriting of German domestic politics,” said Thomas Poguntke, professor of comparative politics at the Heinrich Heine University in Düsseldorf. “But taking the savings breaks a taboo.”

Along with the International Monetary Fund and the European Central Bank, the Germans are sticking to the principle that countries that mismanage their banks and government finances must endure pain as the price of financial help — even if ordinary citizens are the ones who suffer.

Christine Lagarde, the managing director of the International Monetary Fund and one of the officials who worked out the Cyprus plan in Brussels last week, said Tuesday in Frankfurt that she was in favor of changing the plan to burden ordinary depositors less. But she quickly added that Cyprus would still need to contribute $7.5 billion to the bank rescue, as promised.

“Now is the time for the authorities to deliver on what they have committed,” Ms. Lagarde said.

Oxford Economics, a consulting firm based in England, calculated that the uncertainty created by Cyprus could create a credit crunch that could cost the euro zone about 3 percent of gross domestic product, or about $386 billion. It could get worse if the economic dislocation inflamed political unrest in Greece and Italy.

But even if the math seems to speak for granting Cyprus more slack, German leaders will resist abandoning their position in an election year. The European Central Bank is also in a tough spot. Mario Draghi, the bank’s president, took the heat out of the euro zone crisis last year with his promise to buy bonds of troubled euro zone countries as needed to control their borrowing costs.

That guarantee is predicated on the troubled countries’ agreeing to economic restructuring and other conditions. Cyprus shows how hard it could be to enforce such demands, and that could undermine the credibility of the European Central Bank’s promise. Mr. Draghi spoke Tuesday at a conference in Frankfurt, but did not mention Cyprus.

Mr. Draghi has generally been pragmatic rather than doctrinaire in handling the crisis, and has sometimes displeased the Germans. But in this case his bank played a role in pressuring Cypriot leaders to accept a deal. Jörg Asmussen, a German member of the bank’s executive board who took part in the talks in Brussels, told the Cypriots that the country’s banks would no longer be eligible for emergency cash if they did not make a deal.