BRUSSELS (Reuters) - In early May, before the saga over whether Jean-Claude Juncker should become the next president of the European Commission had reached this week's slow-building climax, a pointed question was posed at a briefing in Brussels.
Had it been left up to European Union leaders alone to come up with a Commission candidate, a senior EU official was asked, would Juncker naturally have come top of the list?
The official, who normally avoids answering hypothetical questions, shook his head, acknowledging that the former prime minister of Luxembourg was not the first name on the lips of Europe's heads of state.
Be that as it may, it is too late now - barring a volte-face by Germany or another major surprise, EU leaders will propose Juncker as Commission president at a summit this week, despite staunch opposition from Britain and Hungary.
The anecdote helps illustrate the power shift that has taken place over the past five years as the European Parliament, long derided by critics as a money-wasting talking shop, has seized the initiative from Europe's leaders in critical ways.
By coming up with the concept of "Spitzenkandidaten", German for leading candidates, parliament put itself pole position in determining who gets the influential Commission president post, even though the EU treaty gives it no such power.
Effectively it created a direct link between whichever political group won the European elections held last month and the Commission presidency.
Leaders have since found themselves unable or unwilling to break that link, while the main political groups have tightened their lock by all agreeing to back Juncker - and implicitly no one else.
"This can be seen as a power struggle between the European Parliament and national governments," said Mats Persson, the director of Open Europe, a Eurosceptic London-based think-tank.
"Once the precedent is set, it is unlikely that national governments will be able to claim back this right."
ARM-WRESTLE WITH A TEENAGER
The 2009 Lisbon Treaty increased parliament's powers. As well as a say over the entire EU budget, worth nearly 1 trillion euros ($1.36 trillion) over seven years, it shares legislative authority with the bloc's 28 member states in almost all areas.
The EU assembly does not have the right to initiate legislation, or - crucially - to raise revenue and levy taxes. But it can ask the Commission to bring forward proposals on issues of concern to it, as it did on common euro zone bonds, without managing to budge reluctant member states.
Add to that the "spitzenkandidat" initiative and the fact that whoever is nominated as Commission president must be approved by a majority in parliament and it is clear that the EU's only directly elected body is growing in muscle.
"It's a bit like a teenager that's gone through a growth spurt," commented a northern European diplomat who has been through many bruising negotiations with the assembly.
"It's suddenly got these long arms and legs and a deep voice, but doesn't quite know what to do with itself."
As an indication of the influence it enjoys, Martin Schulz, the legislature's outgoing president who was the Socialists' choice to become Commission president, is now looking to stay in the parliamentary post.
The challenge for those EU leaders unhappy with this trend is to find a subtle way to clip parliament's wings and wrestle back the initiative. If they surrender more powers to parliament now, it will be increasingly difficult to win them back.
One plan is to make the incoming Commission president sign a "strategic agenda" drafted by Herman Van Rompuy, the president of the European Council, in coordination with EU leaders.
The agenda, a draft of which was obtained by Reuters on Monday, sets out broad priorities for the coming years, including jobs and growth, migration, energy diversification, justice and security and the EU's global role.
By signing the agenda, the Commission president would be making a commitment to EU leaders to meet the goals. The critical point being that the priorities will have been set by leaders and agreed with them, not with the parliament.
"At the end of the day, the Commission is there to act in the interests of member states not the special interests of parliament," said a Commission official, himself frustrated by parliament's success in gaining an upper hand.
(Writing by Luke Baker)