KABUL- Opponents facing an uphill battle to unseat Afghan President Hamid Karzai in August 20 elections rallied supporters and sent them out into the streets to put up posters on Tuesday, the official start of campaigning.

Karzai, widely seen as weak and vulnerable earlier this year, has consolidated his authority in recent weeks, persuading some of his leading opponents not to run, winning endorsements from others and leaving the remaining opposition divided.

A newly published opinion survey from last month by a U.S.-based group gave him a wide lead, despite growing public concern about deteriorating security and government corruption.

Forty-one candidates are standing in the second direct vote for a president in Afghan history, seen as crucial in a country which has been at war for decades and faces a spreading Taliban insurgency despite rising numbers of foreign troops.

Candidates include officials and ministers from past and present governments, a former Taliban commander sitting now in the parliament, and two women.

Their supporters began hanging colorful posters on walls and attaching them to vehicle windshields in Kabul and in some provinces on Tuesday as part of the start of the campaign.

Karzai, who has led Afghanistan since the Taliban's ouster in 2001 and won the first presidential poll in 2004, was in Russia attending a summit of regional leaders.

The start of his campaign was announced by Deen Mohammad, a tribal leader from eastern Afghanistan, who resigned as governor of Kabul to oversee Karzai's re-election bid.

RIVALS RALLY

Among Karzai's main rivals, supporters of former Foreign Minister Abdullah Abdullah gathered at a Kabul hotel and dispersed with campaign literature.

Another opponent, Ashraf Ghani, a former World Bank expert and finance minister under Karzai, held a rally at his Kabul villa. He told hundreds of supporters Karzai's government was corrupt and promised to restore Afghanistan's national pride.

The United Nations is helping organize the poll and Western donors, many with troops fighting the Taliban, are paying the $223 million bill, according to election officials.

The survey by the U.S.-based group showed 69 percent of the country had a favorable opinion of Karzai, against 25 percent unfavorable, making him by far the most popular public figure in the country.

He was the most popular choice of voters for president, with 31 percent support, it said. The poll was conducted before the field was set, and his second-place rival with 11 percent support -- a former interior minister -- has since dropped out.

Among candidates registered to stand, Abdullah was second with just 7 percent support, while Ghani had just 3 percent.

The poll of 3,200 adults across Afghanistan also revealed that while most Afghans view the security situation as getting worse they also believe the country is growing more prosperous.

Fifty-two percent said Afghanistan was less stable than a year ago, while just 14 percent said it was more stable. But 53 percent said their family was better off economically than five years ago, compared to just 20 percent who were worse off.

The Taliban, leading the insurgency against some 90,000 Western troops, have called the elections a sham and have vowed to unleash a campaign of violence throughout the next few months.

(Additional reporting by Peter Graff; Editing by Jeremy Laurence)

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