The outgoing Italian Prime Minister bowed out Wednesday, three days after his constitutional reform proposals were booed off by voters.

And just like 'Ol' Blue Eyes', the ambitious 41-year-old exits the stage with his sights on a comeback.

What is uncertain is whether his party or the electorate want an encore from a performer who fluffed his lines when he gambled on the referendum.

Regrets? He admitted he'd had a few when he first said he was going to quit, in the wee small hours of the morning, on Monday.

But by Wednesday afternoon, when he went to President Sergio Mattarella to tender his resignation, he was signalling they were really too few to mention.

He was leaving Italy as a country with “fewer taxes and more rights,” he said in a farewell speech that sounded like an election campaign launch.

Can Renzi return as king of the hill? That will depend on behind-the-scenes discussions within his divided Democratic Party (PD).

In the short-term at least, Italy's youngest ever premier will remain top of the party heap.

But some PD barons are frustrated at being excluded from Renzi's ratpack and with the young leader always wanting to do things his way.

With an election possibly only a little over two months away, Renzi's sure-footedness and popularity are both under scrutiny.

In Sinatra terms, the pledge to quit if he lost the referendum looks like a case of 'Fools rush in where wise men never go …'

Hubris then nemesis 

To Renzi's critics, it was a sign of the hubris that had come to define hi premiership.

Nemesis, when it came, was brutal. Italians massively rejected Renzi's reform plan.

Most worryingly for PD strategists, the poll breakdown also pointed to young voters being most likely to reject Renzi's vision and PD support being eroded in its heartlands.

Renzi seemed to succumb to over-confidence after a prodigious rise.

He was just 39 when he took office in February 2014, using his control of the PD apparatus to orchestrate the ditching of his predecessor, Enrico Letta, days after reassuring him he was safe.

With that coup, Renzi had gone from being mayor of Florence to running the country in just three months. He enjoyed an extended honeymoon after settling into Palazzo Chigi, the premier's official residence in Rome.

Italians seemed to welcome the youthful premier as a breath of fresh air that would blow away the memories of Silvio Berlusconi's unproductive, often embarrassing, years in office.

Drawing inspiration from Barack Obama's “Yes We Can” campaign, Renzi promised far-reaching change and earned himself a reputation as a workaholic.

Burning midnight oil 

His schoolteacher wife Agnese and three children stayed at the family home in Tuscany while Renzi burned the midnight oil in Rome, doing deals to get his reforms through parliament or toiling on the detail of policy initiatives.

But as a sluggish economic recovery failed to gain any real momentum, discontent began to mount and Renzi began to be viewed as part of the problem, not the solution.

It was a turnaround the former Catholic boy scout was not prepared for and even a ringing endorsement from Obama could not lift his flagging fortunes.

Grumbling in his own party culminated in former Prime Minister Massimo d'Alema calling Renzi a Twitter-obsessed “oaf” while the left kept sniping away at what they saw as a dangerously pro-business agenda.

Renzi delivered significant labour market reform, a modest recovery and  oversaw Italy granting legal recognition to gay relationships for the first time.

But the recovery was not strong enough to pay any real dividends politically, the labour reforms have yet to turn into significant jobs growth and critics noted that Renzi had mostly side-stepped the battle over legislation on same-sex civil unions, which was diluted in the end.

Renzi has been a full-time activist or politician since he finished legal studies in his native Florence. But for a brief spell in the family advertising business in his early 20s, it is all he has done and all the signs
Wednesday were that is what he wants to continue doing.

By Angus MacKinnon