WHEN Poland joined the European Union in 2004, says Rafal Trzaskowski, its Europe minister, the old members feared it would be “as terrorising as Spain, as arrogant as France” and as keen on opt-outs as the British. Ten years later and they are more likely to come crawling for advice. Helped by large amounts of EU cash, Poland has become an economic and political role model for the rest of the club, growing by almost 50% over the decade and largely avoiding the lapses into populism or authoritarianism of some others. So it is fitting that this week Donald Tusk, who oversaw much of Poland’s progress as prime minister between 2007 and 2014, should become the first politician from “new Europe” to move into one of the EU’s top jobs. As president of the European Council, where Europe’s heads of government meet, it will fall to Mr Tusk to craft deals between 28 disputatious leaders.

Poland is near the heart of many of the challenges facing the EU, from restarting growth to the Russian threat in Ukraine to the British problem. Some of this is circumstantial: Ukraine is Poland’s neighbour, Britain the top destination for its migrant workers. But it also highlights the maturing of Polish diplomacy. In the early days Poland’s posture was defensive or transactional, concerned with voting rights or the opening of foreign labour markets. That approach persists in occasional “zero-sum” distributional debates, such as those over the EU budget or climate-change policy, that tend to reinforce Europe’s old west-east split. In both cases the Poles won reasonable deals, expanding the budget and gaining exemptions from climate rules.

Elsewhere the Poles have become skilled at wrapping diplomatic initiatives in European colours. The eastern partnership, an (ultimately doomed) attempt to bring the EU’s eastern neighbours, such as Ukraine, into Europe’s orbit without offering them membership, was the product of an odd but fruitful alliance between Poland and Sweden. More recently Poland’s brainy finance minister, Mateusz Szczurek, has pushed a €700 billion ($870 billion) investment plan as a much-needed fillip for Europe’s struggling economies. Trouble abroad is trouble at home, Mr Szczurek notes: the rest of the EU buys 75% of Polish exports.

Poland has learned to move nimbly between different groupings on different issues. The “Visegrad” club (Poland, the Czech Republic, Hungary and Slovakia) is hopelessly split on Russia but united on the need for more cash from Brussels. The “Weimar triangle” (France, Germany and Poland) brings the Poles into the orbit of the EU’s traditional powerhouses, even if its heft is more symbolic than substantial. The relationship with Germany is particularly strong, and rests on two pillars: a shared dedication to fiscal stewardship, and the business ties that have turned Polish firms into important suppliers for German manufacturers.

Beyond the rapprochement with Germany, Poland’s journey to Europe’s core rests largely on its economic success. As ministers never tire of pointing out, Poland was the only EU country not to sink into recession during the financial crisis, an economic achievement from which the country has reaped endless political dividends. One former minister says that in 2007 her European colleagues paid her little heed during trips to Brussels; two years later they were scrambling for her opinions.

Yet despite the happy talk, Poland’s hardest challenges may lie ahead, as a new paper from Piotr Buras, a Warsaw-based analyst at the European Council on Foreign Relations, argues. Since 2004 Poland has banked the easy economic and political wins, spending EU cash on infrastructure projects and reaping the diplomatic fruits of accession. It must now find a new growth model based on innovation rather than cheap labour, particularly as the geyser of EU money dries up. And as the euro zone integrates, the longer Poland hangs on to the zloty the further it may drift from the policy-making core. This is a concern for ministers, for among Polish voters the euro lacks friends.

Enter Tusk

As for Mr Tusk, his appointment tells a story not only about Poland but about the EU. He speaks fluent German but barely any French, unthinkable for a senior EU figure in the past. (His English is stronger, thanks to eight hours a day of homework in recent months.) He supports the euro but has struggled to win over voters. Despite Poland staying outside, he will chair eurogroup summits as well as European Councils, which will please those worried by the EU’s divide between euro ins and outs. He also understands the Russian threat well. Indeed, it was the Ukraine crisis that persuaded him to take the job; just days before the decision in August he was fretting about abandoning his Civic Platform party a year before an election. (He needn’t have worried: the party has bounced in the polls since he left.)

Mr Tusk’s modest predecessor, Herman Van Rompuy, served as a sort of therapist to the EU’s leaders, listening to their concerns and finding common ground where it was available, particularly on economic matters. A different approach may be expected from Mr Tusk, who elbowed his way to the top of Polish politics, sometimes ruthlessly. When appropriate he is likely to make his own views clear, especially on foreign affairs (even if he chooses to leave Europe’s southern neighbourhood largely to the EU’s foreign-policy chief, Federica Mogherini). As a veteran of the anti-communist struggle he can speak authoritatively on the European aspirations of countries like Ukraine.

Yet for all that, Mr Tusk’s tools will be the multilateral ones of a committed European. In particular, look to his plan for an “energy union,” which he hopes will weaken Russia’s ability to play divide and rule among its European customers by creating a single buyer for Gazprom’s supplies. The proposal was a Polish one but would redound to Europe’s advantage. That seems fitting.

Economist.com/blogs/charlemagne