The Daily Telegraph, a conservative British newspaper that takes a dim view of the European Union, published a commentary over the weekend that lamented Mr. Tsipras's "Marxist beliefs" but applauded his refusal "to be railroaded by the corporatist E.U. powers that be."
But the gap between Syriza's self-image as the champion of the underdog and the reality that Europe's least well-off countries have shown it little or no sympathy has exposed a fundamental flaw at the heart of a doomed negotiating strategy that has pushed Greece to the edge of the abyss.
It has also deepened fury in Brussels, the headquarters of the European Union's executive arm, and in Berlin at repeated accusations from Mr. Tsipras that creditors are trying to "blackmail" Greece and upend the democratic choice made by Greek voters in January when they elected Syriza, which campaigned on promises to end years of grinding austerity.
Mr. Tsipras returned to this line of attack in a television address on Sunday evening in which he announced that Greek banks would not open on Monday. Pillorying the European Central Bank for refusing to increase emergency aid to Greek banks, he said the move "had no other aim but to blackmail the will of the Greek people."
Viewed from Bulgaria and other poorer countries in Europe, however, Greece's suffering after five years of painful austerity draws only curt comparisons.
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When Greece's finance minister, Yanis Varoufakis, in an early round of negotiations in Brussels, complained that Greek pensions could not be cut any further, he was reminded bluntly by his colleague from Lithuania that Lithuanian pensioners survived on far less. Mr. Varoufakis shot back that Greeks would never put up with so little.
Lithuania, according to the most recent figures issued by Eurostat, the European statistics agency, spends 472 euros, about $598, per capita on pensions, less than a third of the €1,625 spent by Greece. Bulgaria spends just €257. This data refers to 2012 and Greek pensions have since been cut, but they still remain higher than those in Bulgaria, Lithuania, Latvia, Croatia and nearly all other countries in eastern, central and southeastern Europe.
Such statistics have made it very difficult for Syriza to win support for its argument that Greece is suffering a uniquely painful "humanitarian catastrophe" and that fellow European Union countries should put up their own money to save Athens from bankruptcy.
"Greece is not seen as suffering so much," said Ognyan Georgiev, an editor at Kapital, a Bulgarian business newspaper. "For us it looks very appealing. They have the sea, they have big pensions, and they have a life that looks better than what we have."
This has left Greece isolated not only from wealthy countries in northern Europe like Germany, where public opinion tends to view Greeks as work-shy ingrates, but also from poor countries that also feel put upon and that Syriza had hoped to rally to its side.
Germany, Europe's biggest economy and Greece's biggest creditor, has undoubtedly played a leading role in resisting Syriza's demands for a sharp scaling back of austerity, but it has been joined in this, with a few nuances of tone, by all other members of the European Union.
Raoul Ruparel, co-director of Open Europe, a research group in London, said Syriza was right to focus on the importance of people's democratic choice but had ignored the fact that all governments in Europe have to answer to voters. "Democracy is the crucial point, but this means not just Greek voters but those across Europe," he said.
Greece's creditors and the European Union, he added, certainly deserve some of the blame for the impasse that now threatens to push Greece out of the eurozone, but Syriza made a critical mistake by believing "it could change the economics of Europe without changing the wider political framework."
In an interview with the German public television station ZDF on Saturday, Wolfgang Schäuble, Germany's finance minister, stressed that a referendum called by Syriza on whether to accept bailout proposals might give Greek voters a voice but would not be binding on taxpayers in Germany and elsewhere.
"Imagine the Greek people vote against the will of their government," Mr. Schäuble said. "Then we have to tell our people and our parliaments, 'Now we trust that the Greek government will follow the will of its people, although it just told them to do the opposite.'"
He added, "That is no basis on which to make a decision that comes at the expense of taxpayers of the other European countries."
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After boasting in late February that "we no longer have this unified group against Greece," Mr. Varoufakis, Greece's finance minister, acknowledged in an April message on Twitter that Greece had been left friendless. He cited a 1936 comment by President Franklin D. Roosevelt — "They are unanimous in their hate for me; and I welcome their hatred" — and described it as "a quotation close to my heart (& reality) these days."
In Bulgaria, even politicians who cheered when Syriza came to power in January and who sought to boost their own fortunes by mimicking its tirades against "neo-liberal" orthodoxy have now either fallen silent or sought to distance themselves from the Greek experiment.
Velizar Enchev, a member of Parliament who in April announced that he was splitting from a nationalist alliance to form a new party, Bulgarian Spring, modeled on Syriza, now says that his venture had been misunderstood and that he never really liked Syriza that much.
Ataka, a far-right nationalist party, also praised Syriza for standing up to Brussels when it first came to power but, eager to preserve its own base of support among less educated and poorer Bulgarians, has since offered no support to Greece's demands for more money on better terms from its creditors.
For its part, the Bulgarian government, a center-right coalition that took over from a deeply tarnished Socialist-led predecessor late last year, has given Syriza short shrift.
Speaking in Brussels last week before the start of a European Union summit meeting, Prime Minister Boiko Borisov complained that he was fed up with so much time being spent on Greece's need for bailout funds to pay its bills when other countries have so many problems of their own.
"We, too, want to give more money for salaries and pensions, but we are maintaining this financial discipline," Mr. Borisov said. "I am categorically against delays and compromises" for Greece.