ATHENS — Even in sunny Greece, politics is sometimes for the dogs. Prime Minister Mitostakis and his center-right New Democracy party trounced his chief opponent, Alexis Tsipras, in a nationwide vote on Sunday — but by Thursday Mr. Mitsotakis was no longer officially the prime minister. 

To put a fine point on it, even his adopted mutt had to leave the official prime minister’s residence, Maximos Mansion, to wait out the next few weeks at the New Democracy party’s office south of Athens at Piraeus.

It is not clear if anyone explained to the dog, whose name is Peanut, precisely why Greece has just appointed a caretaker government after a win by Mr. Mitsotakis widely described in the Greek press as “seismic.” Even many non-Greek humans might find it difficult to comprehend why Mr. Mitsotakis, having collected 40.8 percent of the votes at the polls — double that of the radical left coalition led by Mr. Tsipras, with a poorer than expected 20 percent — is no longer officially in power.  

The reason, in its simplest terms, is that despite clinching more than 40 percent at the polls, New Democracy still fell short of the parliamentary majority it needed to keep the government going. The winning party would have needed 46 percent of the total vote to scoop up a majority of 151 seats in the 300-member Greek parliament. 

In an ironic twist, the individual who introduced Greece’s new system of proportional representation is Mr. Tsipras, who served as prime minister prior to Mr. Mitsotakis. 

Mr. Mitsotakis’s landslide victory is now officially frozen, at least until a second election is held, probably on June 25 but possibly sooner. 

On Wednesday, the leaders of the top three parties, which include New Democracy and the far-left Syriza, informed the Greek president, Katerina Sakellaropoulou, that they would not be able to form a single-coalition government. That meant ahead of a new vote they needed to agree on the formation of a caretaker administration. 

That accord coalesced on Thursday with the appointment of a highly respected senior judge, Ioannis Sarmas, as caretaker prime minister. The 66-year-old was sworn in on Thursday. 

The day prior, Ms. Sakellaropoulou told Mr. Sarmas, “I have already announced to political leaders that I plan to propose you among the three presidents [of Greece’s top courts], to present you with the order to form a government that will carry out the elections.”

For Mr. Mitsotakis, what is a slightly bitter start of a presumed second term may be sweeter at the end, because the mechanics of the election next month will be slightly different, in that the winning party will be able to secure additional seats in parliament.

In the run-up to last Sunday’s vote, things were not looking overly rosy for Mr. Mitsotakis. As the Guardian’s Helena Smith wrote, “the once ascendant New Democracy’s popularity [was] hit by a deadly train crash that has taken a wrecking ball to its narrative of effective governance.”

While that was at least partly true, a center-right resurgence is clearly in the cards. The next few weeks leave several ministers in a state of administrative limbo, but in the long run this brief period will likely be seen as something of a blip.

That is because barring an extremely unusual circumstance, there is virtually no way for Mr. Tsipras to reverse his rapidly sagging political standing in the polls ahead of the next vote. Despite being a charismatic speaker, his detractors claimed that as Syriza’s leader he failed to come up with any programmatic action plan. 

Mr. Tsipras had railed masterfully against New Democracy right up to the eve of the election, criticizing it for being elitist and also reminding voters about a recent wiretapping scandal that had been dubbed the Greek Watergate. Yet he failed to leverage voter anger because ultimately many were not that angry: Despite its problems, the Greek economy is on a road to recovery and tourism, the country’s heavy industry, is experiencing a post-pandemic boom. 

Mr. Mitsotakis’s team, in a bid to project a more hip image to disaffected younger voters, launched an aggressive social media campaign that included a liberal dose of TikTok videos to show more the premier’s personal side. That strategy appeared to work. 

Yet because it did, the next few weeks are critical. On Thursday, Mr. Tsipras came out swinging, telling his supporters, “Let’s be serious, we are a party of power.”

Well, that would be diminished power. Another big loser on Sunday was Yanis Varoufakis, the radical left finance minister under Mr. Tsipras whose splinter MeRA25 party failed to garner enough votes to hold on to its seats in the Hellenic parliament. With characteristic invective, he admitted to a group of Greek reporters on Sunday night that “Mitsotakis Ltd. served a crushing defeat,” but he also said that the “Erdoganization and Orbanization of Greece is now complete.”

It is not, of course, but nor is the election drama in this endlessly fascinating and politically complex nation of more than ten and a half million people — plus one little dog that is eagerly awaiting the trip back to his office.