Rival motorcades of political party supporters drove through Cambodia's capital Thursday to kick off the official campaign period for a general election next month that is virtually certain to see Prime Minister Hun Sen, Asia's longest-serving leader, extend his 28 years in power, AP reported. The ruling party and opposition parties both held rallies, each drawing as many as 10,000 people. The July 28 election will be the fifth parliamentary poll since the United Nations brokered a peace deal for Cambodia in 1991, a process meant to end decades of bloodshed that included the communist Khmer Rouge's genocidal 1975-79 rule. Hun Sen, who is 60, said recently that he intends to wield power until he is 74 - cutting back from an earlier vow to stay at the top until he's 90. The iron grip on government held by Hun Sen's well-established Cambodian People's Party gives him major advantages, including the loyalty of the civil service and the power to dispense patronage and other favors. In the last election, in 2008, the CPP won 90 of the 123 seats in the National Assembly. This year, eight parties are contending for the ballots of 9.6 million registered voters.