It isn't meant to matter which party a foreign leader comes from.
When it comes to engagement on the international stage, the national interest tends to trump party political rivalry.
Leaders wouldn't get much done if they only talked to their political mates.
Often, relationships between leaders come down to personality rather than party. Former Prime Minister John Key and President Barack Obama were said to get along well, despite their different political stripes. It was golf, not politics, that brought these two together.
From the first official meeting of Prime Minister Jacinda Ardern and her opposite number, Australian Prime Minister Anthony Albanese, it appears both personality and party have contributed to what could be a strong relationship between the pair, who lead not only their respective countries, but their respective Labour and Labor parties.
The pair know each other from transtasman Labour-Labor circles, and their political outlook means they approach issues in a similar way.
On the Pacific, Ardern restated New Zealand's Pacific-led strategy, which centres on New Zealanders helping Pacific island nations archive their own "aspirations".
Albanese's rhetoric was similar. He said the two countries were in "lockstep" on the Pacific, and articulated a similar strategy based on "transparency" and "trust".
That marks a shift from the previous Australian Government, which earned the rebuke of Solomon Islands Prime Minister Manasseh Sogavare for patronisingly calling the region Australia's "backyard".
Both leaders see opportunity in a less didactic relationship with the Pacific - something the Pacific is keen on.
On climate change, Ardern (though she was quick to say she was "careful" not to venture into domestic climate disputes) was obviously chuffed Australia had decided to up its ambition on emissions reduction.
"Of course, New Zealand is heartened and welcomes the ambition that has been expressed by the new Government here in Australia because it is good for our region and good for the world and we work collaboratively on this extraordinary challenge," Ardern said.
They share a broad view of climate change as an issue that spans economic, diplomatic and environmental portfolios. Albanese hopes taking climate seriously will give Australia some kudos in the Pacific, which could help the country address security concerns in the region. Ardern shares this broad view, and is clearly hopeful Australia's return from what Albanese described as nine years in the "naughty corner" will smooth tensions in the region.
Even on the issue of 501 deportations, which has driven a wedge between Australia and New Zealand, the pair are broadly on the same page.
Indeed, Albanese told a press conference that were he in Ardern's shoes, he would be making the very same appeals she is.
Like Ardern, Albanese appears to see the issue as a social justice rather than criminal justice issue. Also like Ardern, he appears to dislike the law and order populism from which the current 501 policy sprang (though again, like Ardern, he's not afraid to indulge in it from time to time for domestic political gain).
Albanese said he wanted a "common-sense" approach to 501s, and drew attention to "some of the [individual] cases" - an apparent allusion to some of the extreme deportations of people who are Australian in every sense but citizenship.
Albanese said he would "work through" issues around the "implementation of the 501 policy, with any progress likely to be announced when the two leaders and their senior ministers meet next month.
Don't expect dramatic change. Migration is a thorny issue for Australia - it was migration, not Ardern, that was on the front page of powerful newspaper The Australian the morning of Ardern's visit.
Albanese was emphatic the 501 policy would remain, mentioning it multiple times in a fairly brief press conference: "I've said that section 501 would be maintained."
However changes to the implementation of the policy would still be a win for Ardern, and a significant one. Albanese gains very little domestically from adjusting the policy, but Ardern, facing domestic law and order issues of her own, would gain immensely from any change that keeps even a small number of potential deportees in Australia.
The friendship doesn't just extend to the two leaders. Finance Minister Grant Robertson clearly gets on with his opposite number, Treasurer Jim Chalmers.
Chalmers has one of Australia's largest Kiwi expat populations in his electorate, and is apparently well-versed in their concerns and culture.
Robertson gifted Chalmers a copy of former Labour finance minister Michael Cullen's memoir. A good gift to be sure, but it's not the sort of thing you give a Tory, and an indication of the pair's proximity. Chalmers' predecessor, Josh Frydenberg, was a big-picture geopolitics man, a key instigator of Five Eyes finance ministers' meetings which serve little obvious purpose but to further cement Five Eyes' controversial mission creep.
Chalmers is more low-key. He's interested in wellbeing, something Robertson is clearly very keen to talk about.
New Zealand's Government needs to be careful. Australia's coalition Government was difficult to get on with. Its climate recalcitrance made Pacific diplomacy difficult and its enthusiasm for deportation was difficult for any New Zealand Government to embrace.
But quite apart from that, Scott Morrison simply saw the world a very different way to Ardern: wellbeing, social justice, climate change and indigenous self-determination were not on his agenda to the extent they are on Ardern and Albanese's.
It's no secret the two weren't exactly mates. They were far too different for that.
Albanese and Ardern are another matter. The two have at least some relationship from Labour-Labor circles, and the relationship has an obvious warmth. At their first official meeting, Ardern ignored Albanese's outstretched hand and went straight for a warm hug.
Evocatively lit in chiaroscuro, like Caravaggio trying his hand at Gone With the Wind, the official photo of the event looks less like the stale record of yet another bilateral, and more like the poster for a Hollywood romance.
Ardern should be careful, and not look to be getting too close to the Government simply for its political stripes (High Commissioner Annette King, herself a longstanding former Labour MP undiplomatically retweeted images of Ardern's meetings with Albanese and Morrison, which compared Morrison unfavourably).
It's also unclear whether that friendship will translate into clear policy wins. Albanese was guarded on any proposed change to 501s. New Zealand's major diplomatic aims with regard to Australia are in areas that are hotly contested domestically: migration, citizenship and climate.
The strong relationship presents an opportunity for a reset. Relations will not always be this good, and despite the Olympian metabolism of the Australian prime ministership, there's no guarantee future prime ministers will be as amenable to New Zealand's anxieties as this one.
It's an opportunity not to be wasted. No wonder it will be just a month before the pair meet again.