A by-election in a Christian heartland this weekend will take the pulse of Lebanon's sparring factions. Lucy Fielder reports from Beirut Sunday's by-elections in Mount Lebanon and Beirut threaten to be heated and messy, judging by this week's cacophony of mud-slinging and rhetoric from leaders and media representing Lebanon's opposing camps. At stake are two seats vacated by the assassination of MPs Pierre Gemayel and Walid Eido, both from the ruling "14th March" movement. Most Lebanese see the vote in Metn, a predominantly Christian mountain region north of Beirut, as a referendum on the relative popularity of opposition Christian leader Michel Aoun and the "14th March" ruling movement. Former president Amin Gemayel is contesting the seat left empty when his son Pierre was gunned down last November. Metn has been a safe seat for the Gemayel clan for decades and the Phalange Party it founded in the 1930s has its headquarters in the lofty village of Bikfaya. Pierre Gemayel's assassination is likely to rally "14th March" supporters behind his father. Large billboards of Pierre have flanked Gemayel in his rally speeches and Bikfaya held a mass commemorating its dead son this weekend. Nonetheless, the polls' favourite is Camille Khoury, candidate for Aoun's Free Patriotic Movement. Two factions have played tug-of-war with Lebanon since the assassination of former prime minister Rafik Al-Hariri in February 2005 forced Syrian troops to withdraw. Prime Minister Fouad Al-Siniora's government and its supporters pull Lebanon towards an ever more involved United States and accuse Syria of the string of assassinations that have shaken Lebanon. At the other end of the rope, Hizbullah tries to keep Lebanon in an eastern orbit with its allies Iran and Syria. Polls predict the Beirut seat will stay with the Sunni Future Movement of Hariri's son Saad, who heads the "14th March" parliamentary majority. A car bomb killed Hariri ally Walid Eido in June on the seafront in Beirut and the favourite to replace him is Mohamed Amine Itani. Of Lebanon's major sects, the Sunnis are overwhelmingly behind Hariri, the Shia behind Hizbullah, and the numerically small but politically significant Druze minority follows "14th March's" Walid Jumblatt. Only the Christians are significantly divided. Aoun's alliance with Hizbullah endured Israel's bombardment of Lebanon and the ensuing internal blame- game -- with a significant proportion of Lebanese blaming Hizbullah for drawing Israel's fire by kidnapping two Israeli soldiers in a cross-border attack last July. Most observers believe the axis has cost Aoun Maronite support but he remains the single most popular Christian leader, ahead of far-right Lebanese Forces leader Samir Geagea, a "14th March" leader. Abdo Saad, head of the Beirut Centre for Research and Information, said a poll he conducted on Friday forecast a clear win for Aoun's Free Patriotic Movement. "But it's not easy to predict in a volatile area such as Metn, it could all change," he said. Twenty per cent of Metn voters have no political affiliation and could go either way, he said. And in shock-prone Lebanon, major upheaval before then is always possible. Saad said he was unable to release the results of the privately commissioned poll, but the margin was clear. For Gemayel to change the result, Aoun's allies, MP Michel Murr and the Armenian party Tashnaq, would need to renege on their promised support and the former president would need to attract 70 per cent of independents. "I would be surprised if the tayyar [Aoun's FPM] didn't win," he said. Aoun and Gemayel traded insults this week and rival supporters kicked, punched and beat each other with sticks on the streets northeast of Beirut. Gemayel described Aoun as pro-Syrian and his alliance with Hizbullah as an "alliance against nature", depicting the by- election as a "struggle for Lebanon's survival". Aoun responded by slamming the former president as a "failure" as a politician. "Not you, nor anything you boast of reaches to below my waist level," he said. Aoun has contested the constitutionality of the election because Prime Minister Siniora signed off on it after pro-Syrian President Emile Lahoud refused. After a Free Patriotic Movement legal appeal against the election failed, Aoun decided against a threatened boycott and put Khoury's name forward. However, he still portrays the contest as a battle against the violation of the constitution. The constitutional council was re-considering the validity of the election at the time of writing. Aoun would consider the cancelling of the election a victory as much as winning the seat said Charles Harb, an American University of Beirut psychology professor and political analyst. "But if Aoun wins he'll be able to say the candidates that Hariri is putting forward lack credibility. It would put a serious dent in the '14th March' if Gemayel does not get re-elected in his own constituency." A fierce battle for Lebanon's presidency looms in September. Former general Aoun has long had his eye on the post, traditionally reserved for a Maronite Christian under Lebanon's sectarian system. Gemayel, who was president with US backing from 1982-88 at the height of the war, may be planning to stand again. "This by- election will strengthen the hand of the winner for the presidential elections," Harb said. He described the relationship between Aoun and Gemayel as a "tumultuous history" of "marriage ending in divorce". The two were allies during Gemayel's presidency, and in 1988 it was he who appointed Aoun, then commander of the army, as prime minister, despite the Sunni claim to that position. Parallel governments and Aoun's doomed military campaign against the Syrians were to ensue. But the two have squared off in the political dispute of the past two years. Maronite divisions have rattled Patriarch Nasrallah Boutros Sfeir, who sees them as diminishing the clout of the traditionally powerful sect. He urged his followers to unite this week and appeared to hint that Aoun should bow out by pointing out the seats in question belonged to assassinated MPs. He called for the by-election to be postponed or a "consensus" MP found. Khaled Saghieh wrote in the independent, pro- opposition Al-Akhbar newspaper last week that the patriarchate usually pleaded for "unity of the ranks" at times of electoral battle. It appeared that the patriarch was "jealous" of the other major sects, which have overwhelmingly adopted one opinion and one leader, he said. "Thus, the Maronite patriarch came up with a special recipe that includes democracy but without threatening the unity of the ranks. What does this mean? It means simply that the Christian political leaders have no role to play and the differences and disagreements between them are secondary to the higher interests of the sect, determined by the church and its master, the patriarch from Bkirki," Saghieh wrote.