Antoine Ghanem, a 64-year-old member of the Christian Phalange party who had returned from refuge abroad only two days earlier, was the eighth anti-Syria figure and fourth lawmaker from the governing coalition to be assassinated in less than three years.
Coalition members blamed Syria. Damascus denied involvement, as it has for the previous seven assassinations, including the 2005 bombing death of former prime minister Rafik Hariri -- a killing that ignited huge protests that forced Syria to withdraw its troops after a three-decade occupation.
Security officials said at least 67 people were wounded in Wednesday's blast, half of which had left the hospital by day's end. The explosion occurred at rush hour on a busy street in the Sin el-Fil district, severely damaging nearby buildings, setting several cars on fire and scattering blood and debris along the street.
Explosive experts were seen checking the engine of Ghanem's car, which was thrown more than 150 feet. A security official said the bomb was likely detonated by remote control near Ghanem's car.
"I have never seen a more cowardly regime than that of Bashar Assad's," lawmaker Saad Hariri said, blaming the Syrian president for Ghanem's death. Hariri replaced his father, the assassinated ex-premier, as head of anti-Syria forces, which now hold a majority in Parliament.
Cabinet member Ahmed Fatfat also blamed Syria for the attack, saying Damascus wanted to derail efforts by majority and opposition leaders to reach some accommodation as they begin presidential voting in Parliament on Tuesday.
"It is the only regime that does not want presidential elections in Lebanon to be held," Fatfat said.
President Emile Lahoud, an ally of Syria, also implied Ghanem's death was meant to undermine the presidential vote, saying "it is no coincidence that whenever there are positive signs" that someone is killed.
Syria said the attack was aimed at sabotaging efforts by the Lebanese people to reach agreement.
"This criminal act aims at undermining efforts paid by Syria and others to achieve Lebanese national accord," Syria's state-run news agency SANA quoted an anonymous Syrian official as saying.
Many people fear the divisions over the presidency could lead to creation of two rival governments, a grim threat to repeat the last two years of Lebanon's 1975-90 civil war when army units loyal to competing administrations battled it out.
The United States has accused Syria of trying to undermine Lebanon's government, but has stopped short of tying the Damascus regime to the political killings.
"The bombing that claimed these lives was another in a campaign of terror by those who want to turn back the clock on Lebanon's hard-won democratic gains," Secretary of State Condoleezza Rice said in a statement. "Enemies of peace and freedom want to gain through violence, threat, and intimidation what they cannot win in free and fair elections."
The assassination of anti-Syria figures began with the killing of Hariri on Feb. 14, 2005, in a bombing that killed 20 other people. Mammoth demonstrations coupled with international pressure forced Syrian troops to leave, and Lebanese elected a government led by anti-Syria politicians.
Since then, U.S.-backed Prime Minister Fuad Saniora has been mired in a power struggle with the opposition, led by the Syrian-allied militant group Hezbollah. Government supporters accuse Syria of seeking to end Saniora's small majority in Parliament by killing off lawmakers in his coalition, which now holds 68 seats to the opposition's 59.
With the loss of Ghanem and the earlier killing of Pierre Gemayel, the Phalange party -- one of the main political and military powers during the 1975-90 civil war -- was left with just one representative in Parliament.
After the assassination of lawmaker Walid Eido in June, many majority legislators left the country to spend the summer abroad in safety, while those who stayed took extra security.
Fatfat, the Cabinet member, told the AP that Ghanem had just returned Monday from an undisclosed country where he took refuge for two months.
Ghanem was traveling Wednesday in a car with regular license plates, his blue Parliament plate hidden in the trunk, apparently as a security measure.
Antoine Andraos, another colleague, said Ghanem had called him earlier in the day asking for a bulletproof car, a TV station linked to Hariri reported.
Security officials, meanwhile, said a landmark hotel near the Parliament building in downtown Beirut has been rented to house legislators in the governing majority so they can be better protected during the 60-day presidential election process.
Lahoud is due to step down from the presidency by Nov. 23, and government supporters see the vote as the opportunity to put one of their own in the post.
But Hezbollah and its allies vow to block any candidate they don't approve -- and they can do so by boycotting the ballots, preventing the needed two-thirds quorum of 85 votes.
If no candidate is agreed on by the time Lahoud steps down, Saniora and his Cabinet would automatically take on executive powers. If that happens, opposition supporters have said Lahoud might appoint a second government, a step many fear would break up the country.