The centre-left coalition led by Democratic Party (PD) leader Pier Luigi Bersani has been leading in the polls since the start of the campaign. A phlegmatic former minister, Bersani saw his leadership of the left sanctioned by a convincing victory in primaries last year, in which almost three million Italians turned out to vote. His coalition, known as "Italy, Common Good", includes the more left-wing Left, Ecology and Freedom (SEL) and numerous minor parties, such as the German-speaking Südtiroler Volkspartei that polls in north-eastern areas bordering with Austria.
Bersani, 61, has pledged to maintain the budgetary discipline of Mario Monti's technocratic government, while also stepping up efforts to boost growth and create jobs. Victory in the lower house of parliament would make him the favourite to lead the next government, but a tight race for the Senate means he may have to seek a coalition with Monti's centrists - a prospect analysts say could lead to an unstable government and fresh elections in the coming months.
Weakened by defections, repeated scandals and Silvio Berlusconi's abortive retirement, the People of Freedom (PDL) party is no longer the formidable war machine of old. But the sudden return to politics of the three-time former prime minister has revitalised the party and denied the left a comfortable win. Having scrapped the PDL's planned primaries, Berlusconi has cobbled together a centre-right coalition with his traditional - albeit reluctant - partners of the Northern League and a host of smaller parties, including the Great South party of convicted Mafia accomplice Marcello Dell'Utri.
Berlusconi, 76, has been highly critical of Mario Monti's austerity measures, vowing to slash taxes and reimburse Italians for a deeply unpopular property tax. A whirlwind tour of television sets has helped him close the gap in the polls, but his coalition still trailed the left by some 5% when a ban on opinion polls came into effect two weeks ahead of the vote. The "Cavaliere" has said he is not aiming for a fourth term as prime minister, suggesting he might serve as finance minister instead.
If his European peers were to vote, Italy's outgoing prime minister Mario Monti would be a shoe-in to lead the next government in Rome. But the austere policies and demeanor that have made him the darling of Brussels have not endeared "'Supermario" to tax-burdened Italians. Well aware of this likeability gap, Italy's 69-year-old technocrat-in-chief has hired Barack Obama's campaign strategist David Axelrod to burnish his credentials as a politician.
While it is too early to tell whether the strategy has paid off, analysts say Monti's best chance of entering the next government is as a junior partner to the left. His centrist coalition, known as "Civic Choice - With Monti for Italy", includes the Christian Democrats (UDC) and the centre-right Future and Freedom for Italy (FLI) led by the speaker of the lower house of Parliament, Gianfranco Fini. It is vying for third place with the 5-Star Movement of firebrand comedian Beppe Grillo.
One candidate who could yet spoil everyone else's plans is outspoken satirist Beppe Grillo, whose anti-establishment 5-Star Movement (M5S) has been riding a wave of popular discontent aimed both at traditional parties and Mario Monti's technocratic government. Grillo, who is not running for office himself, has called for Italy's politicians to be "sent packing" and has ruled out making alliances with other parties.
While others have largely fought their campaign on television, Grillo has mostly shunned the media, instead braving the bitter winter cold with his "Tsunami Tour" - a series of open-air rallies that have drawn ever larger crowds in cities and towns across the country. Helped by a wave of corruption scandals involving politicians from across the political spectrum, the 5-Star Movement has surged in the polls and threatens to deny both the right and the left a majority in the Senate.
Like Beppe Grillo's 5-Star Movement, the Civic Revolution led by high-profile anti-mafia magistrate Antonio Ingroia is largely a citizens' movement, though it also enjoys the support of several minor left-wing and green parties. Backed by Naples's maverick mayor Antonio De Magistris, Ingroia's list threatens to take precious votes away from Pier Luigi Bersani's centre-left coalition, particularly in the key Campania region around Naples.
On the opposite side of the political spectrum, Stop the Decline, a movement founded by a group of right-leaning economists and led by journalist Oscar Giannino, could inflict similar damage on Berlusconi's centre-right coalition in the battleground region of Lombardy.