Italy's Prime Minister Enrico Letta gestures as he leaves his house in downtown Rome February 14, 2014. Italian centre-left leader Matteo Renzi forced party rival Letta to resign as prime minister on Thursday after criticizing his government's failure to pass major reforms, opening the way for Italy's third administration in a year. [Photo/Agencies]

DEFICIT OVERSHOOT

Renzi espouses market-friendly policies like reducing public spending and taxes, cutting red tape and easing firing restrictions. He has also said that while pursuing structural reforms Italy should allow its budget deficit to exceed European Union limits.

He is backed by a large part of Italy's industrial and financial elite, though he has no experience of national government and his policy prescriptions remain vague.

Since his landslide victory in the PD primary in December, Renzi, a former boy scout who began his political career in a now defunct Catholic centrist party, has never been out of the headlines.

He moved fast to try to broker a cross-party deal on a reform of electoral rules blamed for Italy's chronic political instability, and those proposals are now before parliament.

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He has also shown considerable steel in consolidating his grip on the PD by facing down internal dissent from the leftist arm of the party which has always campaigned against him.

But at the same time he systematically weakened Letta and his government with constant sniping from the sidelines, blaming the prime minister for moving too slowly to reform the euro zone's most sluggish economy over the last decade.

Renzi could hardly be more different from the solid but dull Letta and the two men have a thinly veiled disdain for each other despite both coming from the centrist, Catholic arm of the PD rather than the larger left-wing component.

It was widely thought that Renzi wanted to broker a deal on electoral reform and then win an election in 2015 - when Letta had repeatedly hinted he would step down - at the head of a strong majority that would allow him to govern effectively.

His change of strategy suggests he either thinks he can do better than Letta at the head of the same fragile left-right coalition, or he believes he can change the coalition to include parliamentarians from parties currently in opposition.

He has appealed to lawmakers from the anti-establishment 5-Star Movement to abandon their hard line opposition and support PD legislation.

Renzi is certainly not afraid to make enemies and rode roughshod over protests from shopkeepers and motorists to pedestrianise the historic centre of Florence.

He may find it much harder to trample down the web of political resistance and vested interests that have hampered economic reform at the national level for decades.