It started out as general ambivalence. Some sympathetic and vocal Germans helped it along towards enthusiasm, and it peaked at raucous, flag-waving delight when Robert Lewandowski scored the tournament's opening goal.
Just about favourable was probably where the goodwill-o-meter of Ukrainian supporters in Lviv had finally settled by the end of Poland's match against Greece.
Which is better than it might have been. Qualified support for neighbours with whom they share a storied past was never a given. It beats fear and loathing any day.
In a tournament that threatened to be irrevocably sullied by nationalism even before a ball was kicked, a city regarded as the seat of Ukrainian patriotism was happy enough to temporarily swap its allegiance last night.
In this part of Europe, grudge matches extend far beyond player squabbles or basic local bragging rights. These are serious enmities stemming from histories of bloodshed.
Lviv lies just 62 kilometres along the E40 motorway from the Polish border. For much of its history it was under Polish rule, before the Second World War purged most of the Poles who had made up 65 per cent of the population.
There is no doubting its identity now. Where Russian predominates in cities like Kiev in the north and Kharkiv in the east, Ukrainian is the language of choice here.
The fan park built for this tournament in the Prospekt Svobody (Freedom Avenue) is adjacent to a towering statue of Taras Shevchenko, the father of the language.
Symbols of patriotism do not come much more obvious.
To extend the theme to the football pitch, the Ukraine national team have never lost a match they have played in Lviv.
Yet the local people were still content to adopt their nearest neighbours on Day 1 of the tournament they are sharing.
"I have been to Poland and people there said I was their friend because I am from Lviv. They see it as their town," said Kiryk Taras, owner of a small business here.
"We are similar people and we understand each other's language. Poland want us to join them in the European Union and we have co-operated with them in staging Euro 2012. So I think most people in Lviv want to see them do well."
There is good reason Polish football fans might hold this city in high regard.
The Polish Football Association was founded here and the national team played their first three home matches in what was then known as Lwow.
One of the most successful clubs of Polish football's early days were from this Ukrainian city. In 2009, Pogon Lwow, who won the Polish league four times in the 1920s, was revived after a 70-year hiatus.
They now play in the region's amateur leagues, picking players from the small Polish community that still exists here, as well as Ukrainians.
"Pogon Lwow is a symbol for all Polish people," said Michael Czwornog, who founded Pogon's supporters club four years ago, before there was even a team to support again.
He says he will be firm in his support of anyone but Ukraine in this tournament.
"Lwow is a magical city for every Polish man. Pogon Lwow is for Polish supporters like a second national team."
The idea of nationality in central and eastern Europe is not what it one was.
Germany's strike-force tonight against Portugal at the Arena Lviv, for example, is likely to be led by two Poles, in Miroslav Klose and Lucas Podolski.
The Germans at Lviv's fan park yesterday were overwhelmingly in favour of Poland, drumming tunes on recycling bins and chanting: "Polska, Polska!"
Whether Polish supporters return the gesture to their neighbours - and specifically their fellow hosts - remains to be seen, though.
"Polish people always co-exist well with all neighbours," Czwornog said, before adding a telling rider. "When Ukraine will play against England I will support the England team."
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