ATHENS — Demonstrators projected the word across the facade of Parliament last week, and it underscored the hurdle that Prime Minister George Papandreou faces in selling an increasingly resentful electorate on a tough new round of austerity measures: “Thieves.”

Most Greeks say they have little confidence in a political class that they see as corrupt and unaccountable. A recent study by Transparency International in Greece found that 9 out of 10 Greeks believed that their politicians were corrupt, and 80 percent said that Parliament had lost credibility.

“We’re here because we have lost confidence in the present political system, which has brought us to the edge,” Christos Siveris, 35, said last week as he waved a Greek flag outside Parliament during a crucial confidence vote, which Mr. Papandreou won. “This is our Thermopylae,” he added, referring to the ancient battle in which an outnumbered army of Greek warriors held out against a Persian force before ultimately succumbing.

This week Mr. Papandreou will seek parliamentary approval for an austerity package that was agreed on Thursday with European officials and the International Monetary Fund. He is expected to succeed, despite tensions within his Socialist Party and in the face of intransigence from the center-right opposition, which was in power when Greece’s debt soared.