His age counted in his favour amid calls for a generational turnover, as did his "post-ideological" image which makes him an ideal guarantor for a grand coalition government.
Despite his age, Letta has already served in four governments, including stints as minister for Europe and for trade and industry starting in centre-left cabinets from the late 1990s.
Another possible asset for the current political situation is the fact that his uncle is Gianni Letta, a shadowy figure who has been Silvio Berlusconi's right-hand man for years.
This did not prevent him from being one of Berlusconi's strongest critics, although the scandal-tainted billionaire tycoon will now be an important power behind the throne.
Letta was born in Pisa on August 20th, 1966 and studied political sciences and international law at a time when he was an active member of the Christian Democratic party, which eventually collapsed in a storm of corruption scandals.
Letta headed up the European youth wing of the centre-right Christian Democrats between 1991 and 1995, after which he worked at the finance ministry on Italy's bid to adopt the euro before joining Massimo D'Alema's leftist government in 1998.
The ambitious Letta later served under two other prime ministers - Giuliano Amato and Romano Prodi in a period in which an often divided centre-left alternated its frequently brief terms in office with successive Berlusconi governments.
He has said his heroes are Polish anti-communist leader Lech Walesa and South African anti-apartheid icon Nelson Mandela.
Letta has also admitted to a fondness for popular Italian comic "Dylan Dog" - the adventures of a womanising sleuth specialised in the paranormal.
"I wanted to be like him," he told one interviewer. Letta is also a big fan of British rock band Dire Straits and Italian pop-rockers Nomadi.
He has been a leading member of the national committee of the Democratic Party since it was formed in 2007 as a combination between the remnants of the
historic Italian Communist Party and a series of small centrist parties.
But he sees himself as "post-ideological" saying in one interview in 2007: "My generation did not live through certain illusions and has therefore avoided the period of disillusionment".
He said his first public speech was a denunciation of the Soviet invasion of Afghanistan during a protest when he was still at school.
Letta failed in his bid to take over the leadership of the Democratic Party in 2007, although he became deputy leader in 2009.
He is currently the most senior figure in the party after its senior leadership resigned on Friday following a rebellion within party ranks during voting on a new president.
Letta is the author of a few books including "Building a Cathedral: Why Italy Should Go Back to Thinking Big" and "Is Europe Over?" in which he called for a "new project" for Europe to lift it out of a period of crisis on many levels.
He has been married twice and has three children.