Mr Juncker served nearly 19 years as prime minister of Luxembourg and was one of the architects of the euro, before finally being ejected last December.
So it is hardly surprising that he was regarded by many - although not by David Cameron - as a natural choice to become the next president of the European Commission.
The 59-year-old is seen as slightly to the political left of the European centre-right mainstream and has been a skilled fixer and bridge-builder at the heart of the monetary union for 25 years.
The only leader still active to have been at the table at the 1991 Maastricht summit that laid the foundations of the euro, he faces a daunting challenge to restore public confidence in European integration and hold the EU together.
The son of a Luxembourg steel worker, Mr Juncker went on to study law and get his first ministerial job at just 29. He has argued that his rise would not have happened without protections that helped his father's job security.
"If my father had had to fear for his job every six months, I would never have seen the inside of the Strasbourg law faculty," he told a small group early this year, saying that had convinced him of the need to curb flexible work contracts.
Mr Juncker has also supported a minimum wage across the EU.
However, he is generally held to be a pragmatic deal-maker and power broker rather than an out-and-out ideologue.
He was central to the fraught negotiations over the 1997 Stability and Growth Pact that originally underpinned the eurozone, a fact that hardly recommends him to Eurosceptics in the UK.
In 2005, Mr Juncker was heavily involved in amending that rulebook after Berlin and Paris broke the deficit limits.
When the eurozone descended into crisis in 2008, again it was Mr Juncker at the heart of efforts to ensure its survival, from Greece's bail-out to forging a banking union across member states.
His nomination for the top job revived questions about his lifestyle, notably his heavy smoking habit and his alcohol intake.
The drinking habits of a man widely reported to like "a cognac at breakfast" were raised as a concern during the diplomatic tussle, one diplomat said.
People who have worked closely with Mr Juncker have also questioned how this sometimes irritable man will cope with the management challenge of running a large bureaucracy and a big personal staff, and whether he has the stamina for the constant travel and speech-making imposed by the role previously held by Jose Manuel Barroso, a former prime minister of Portugal.
His task will not be eased by Mr Cameron's branding him the wrong man at the wrong time, and objecting that his nomination was the result of an illegitimate power grab by the European Parliament.
Assuming EU lawmakers confirm him in a July 16 vote in which he seems assured of a majority of centre-left and centre-right deputies, his five-year term may be dominated by Mr Cameron's efforts to renegotiate Britain's relationship with the EU before a referendum he has promised in 2017 that will give voters the chance to quit the bloc altogether.