Under the terms of the deal, Greece’s private lenders will agree to write down 100 billion euros of Greek public debt and take a loss of more than 70 percent in exchange for longer-term bonds. “I wonder what would be happening today in Greece, in the euro zone and in the global economy if a deal had not been reached, what prospects there would be for banks, for savings, for the wages of Greeks,” Mr. Venizelos said.

But many Greeks were not buying it. “In my simple mind, it seems crazy,” said Dionysius Tsoukalas, 35, as he served customers at a downtown Athens coffee bar. “They took off 100 billion, but now we took a new loan for 130 billion. Why would we do that? It’s crazy.”

Mr. Tsoukalas said he had a master’s degree in industrial product design but worked in the coffee bar five days a week to make ends meet. He said he earned around 700 euros a month, or about $927, and could barely get by, with his mortgage and new tax increases.

He was upset that Greek politicians had not followed through on their plans to make structural changes. “In two years they haven’t done anything,” he said. “They didn’t open the closed professions, they didn’t touch the cartels,” he added, referring to the powerful groups that control the import of consumer goods in Greece’s import-driven economy.

Privately, Greek and European officials said they did not believe that Greece’s increasingly weak political class would have the will or the time to carry out the new austerity measures, which they say require complex legal expertise and cooperation among ministries in a state that lags in administrative capacity.

Parliament already approved the measures in principle and is expected to pass specific implementation bills before the end of the month, even amid growing concern among Parliament members that the measures will push the country further into recession. At the same time, politicians are fighting for what little political capital they have left after two years of austerity has drained them of popular support.

Growing political instability is another wild card affecting Greece’s public finances. Opinion polls say that the center-right New Democracy party is leading in the polls, but that combined, left-wing parties that are opposed to the loan agreement also have significant support.

On Tuesday, Antonis Samaras, leader of New Democracy, who has been pushing for elections and is the front-runner to become the next prime minister, said the new agreement “eliminates the risk of bankruptcy for the country, secures its prospects within Europe, creates the possibility for debt to become sustainable, and opens the road for elections.”