* Leader's control of party machinery likely to prove decisive
* Unglamorous campaigner counting on experience to win
* Pledges to keep tight budget rein, give more help to workers, poor
By James Mackenzie
ROME, Nov 22 (Reuters) - According to a popular YouTube parody, supporters of Pier Luigi Bersani, leader of Italy's Democratic Party, are the kind of people who mentally convert euros into lira, grip the steering wheel while driving and try, in vain, to break up fights.
But for all his image of slightly hapless decency, the 61 year-old former communist, who has led Italy's biggest centre-left force since 2009, is favoured to become its candidate for prime minister in next year's election.
The son of a mechanic who ran a small petrol station near the northern city of Piacenza, Bersani has little of the media-friendly aura of Matteo Renzi, the smart young mayor of Florence who is his main rival in the race.
Bald, plainly dressed and regularly seen with a stumpy Tuscan cigar clenched between his teeth, his rumpled air is the opposite of the template for image-conscious, centre-left reformers set by Britain's Tony Blair.
But in a profoundly conservative country like Italy, a homespun manner does not necessarily hurt and in any case, Bersani has one big advantage, his control of the Democratic Party (PD) machine.
The party is not the platform of a single, charismatic leader like Silvio Berlusconi's People of Freedom party but its chief must still manage its competing factions and interests and Bersani's rivals are no match in that respect.
"This isn't about appealing to voters, it's about appealing to the party and Bersani has the party in his hands," said one PD official, who spoke on condition of anonymity.
A career politician, Bersani is the only one of the five candidates in Sunday's centre-left primary to have served as a government minister and is pitting his experience against Renzi's image as a modernizer.
He is regularly denounced as an ex-communist by his opponents on the centre-right and his wider electoral appeal is perhaps less than Renzi's but his record does not suggest any radical shifts in policy if he became prime minister.
A well-regarded industry minister under former Prime Minister Romano Prodi in the 1990s, Bersani pushed some of the same kind of moves to open up the economy to more competition later undertaken by Mario Monti.
He has supported Monti's technocrat government while it passed a series of tax hikes, spending cuts and labour market reforms that were bitterly resented by his union allies.
Like Renzi, he has also pledged to respect Monti's commitment to cut Italy's budget deficit and says he will not stick blindly to growth-sapping austerity measures but will also help workers, students and pensioners suffering in the slump.
When Bersani was first appointed minister in 1996, the parish priest in his home town of Bettola rang the church bells in celebration, an unusual thing to do in a town that traditionally voted for the centre-right.
Assuming he gets through the primary and a likely second round runoff on Dec. 2, Bersani will be hoping that he can achieve a similar appeal across party lines with voters in next year's national election.