Foreign auditors are to meet next week in Greece for a post-bailout review, with talks expected to focus on the enduring problems of Greek banks and their nonperforming loans, as well as taxation.

The catalyst for the challenge to Mr. Tsipras’s government was a proposal to rename the neighboring nation of Macedonia. Greece had long blocked Macedonia from joining NATO, insisting that the country’s name implied territorial claims to the Greek region called Macedonia.

Last year, the two nations signed an agreement for Macedonia to change its name to North Macedonia. The Macedonian Parliament approved the name change last week, and the Greek Parliament is to consider it in the coming days.

But the proposed change does not go far enough for many, including the Independent Greeks, who cited it in quitting the government. Thousands took to the streets of Athens and other cities to protest the deal last year, and a rally is planned on Sunday.

Some people have gone beyond protest. This week, a 63-year-old retired naval officer was arrested on charges of sending threatening messages to a government official over the Macedonia agreement.

Over the weekend, a top prosecutor launched an investigation into reports that several lawmakers had received threats warning them not to back the deal. And the police in northern Greece said on Wednesday that they had arrested four people over “wanted” posters targeting Greek lawmakers who support the name change.

Despite the upheaval, officials have expressed confidence that the Macedonia deal will pass with the support of opposition and independent lawmakers. But the outlook appeared unclear after the centrist party Potami, which had originally indicated it would back the pact, said it was reviewing its stance.