PHOTO: REUTERS
Lawmakers will convene at noon (1000 GMT) for their 46th attempt to elect a president but the first expected to actually produce a result.
Security was tight around the parliament and Beirut's Martyrs Square, where supporters of Aoun's Free Patriotic Movement (FPM), dressed in their trademark orange, have been gathering for days.
The 81-year-old former general has long eyed the presidency, and his candidacy was backed by the powerful Shiite Hezbollah movement, his ally since a surprise rapprochement in 2006.
But the key to clinching the post has been the shock support of two of his greatest rivals: Samir Geagea, leader of the Christian Lebanese Forces, and Sunni former premier Saad Hariri.
Hariri described his endorsement of Aoun as necessary to "protect Lebanon, protect the (political) system, protect the state and protect the Lebanese people".
The streets of the capital were emptier than usual ahead of the vote, with most schools and universities closed, but Aoun's supporters were out in force.
"We're counting the minutes until General Aoun is elected, we've waited a long time," said Jean, a 35-year-old hairdresser in the Dekwaneh neighbourhood outside Beirut.
"I'm going to close the salon after he's elected and go to downtown Beirut to participate in the celebrations which will last until dawn," he told AFP.
In the Jdeideh suburb of Beirut, dozens of supporters dressed in orange waved pictures of the stern-looking Aoun, as his party's anthems blared from loudspeakers.
"We have won. Lebanon has returned to us," said Indira Georges Alwan, dressed in orange.
The anticipated election was also being celebrated in Syria, despite Aoun's historical antipathy to Damascus.
He once waged a war to push Syrian forces out of Lebanon, but in 2006 joined hands with Hezbollah, a key ally of Damascus that has dispatched fighters to bolster the regime against a rebellion.
"The resistance axis has triumphed, Syria and its allies in Lebanon have triumphed," trumpeted the Al-Watan daily, which is close to the government.
Nicholas Sehnaoui, Lebanon's former minister of telecommunications and a member of Aoun's FPM, echoed many supporters in describing the election as a "dream (that) has come true."
"He will be a president for all the Lebanese, not just his party," he told AFP.
Sehnaoui expressed hope Aoun would be elected in a first round vote in the parliament, which would require him to win a two-thirds majority of 86 lawmakers.
If he fails to secure that, the vote will go to a second round, where he needs only a 50-percent-plus-one majority of 65 votes, a figure he seems to be assured.
His biggest adversary in parliament will be speaker Nabih Berri, who has said the 13 votes from his Amal party will not go to Aoun.
Ali Khreis, an MP in Berri's bloc, told AFP he would cast a blank ballot in protest at the horsetrading that secured Aoun's candidacy.
"A blank ballot is an objection to the way things were done, a method that I think is wrong. This country doesn't run on bilateral or trilateral agreements -- we believe in dialogue," he said.
Aoun is expected to nominate Hariri to return as prime minister, leading some to describe his support for the ex-general as a tit-for-tat.
Aoun's detractors have ramped up criticism of him ahead of the vote, accusing him of allying with whoever will help advance his interests.
In footage posted by an opponent, Aoun is heard railing against the same parliament set to elect him on Monday as an "illegitimate" body because it has twice extended its own mandate.
While Aoun's election will end a vacuum seen as damaging for the country, experts say it is unlikely to resolve the underlying disagreements that kept the post empty for so long.
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