KABUL, Afghanistan -- Abdullah Abdullah, the front-runner in Afghanistan's presidential election campaign, announced Sunday that he had won the endorsement of Zalmai Rassoul, the third-place candidate, as part of his effort to gather enough votes to win in the next round of voting.
Together the two men's tickets took about 55 percent of the vote in the first round of voting April 5, but there is no guarantee that voters would vote the same way in a second round, tentatively set for June 14.
Mr. Abdullah's camp as well as some analysts worry that a runoff could be rife with fraud and that there is more risk that it could be disrupted by the Taliban. The insurgents' campaign of violence failed to have much effect in the first round, but the Taliban could redouble their efforts to intimidate voters in a second.
Mr. Abdullah won nearly 44 percent of the vote in the first round, followed by Ashraf Ghani with nearly 33 percent and Mr. Rassoul with 11 percent, according to the most recent count by the Independent Election Commission of Afghanistan. The final results for the first round are expected later this week, according to the election commission.
Mr. Ghani, who came in second, has repeatedly said that there needs to be a runoff as mandated by the constitution. Some commentators believe that a second round of voting would split along more ethnic lines, which could benefit Mr. Ghani, a Pashtun, since Pashtuns represent a plurality of the population. Mr. Abdullah is most closely associated with the Tajik ethnic group.
While both candidates have tickets that include two vice presidents, each representing other ethnic groups, it is the top of the ticket that gets the most attention when it comes to factional affiliation.
Mr. Rassoul was believed to be the favored candidate of President Hamid Karzai, but Mr. Karzai was careful not to endorse anyone and kept a low profile during the campaign.
In an announcement to a packed news conference at the Intercontinental Hotel in Kabul, Mr. Rassoul described Mr. Abdullah as "a good colleague" whom he had known for a long time and worked well with, adding that "our commitment to the people of Afghanistan is to avoid the ethnic rift."
Wearing white shalwar kameez, Mr. Abdullah spoke fervently to the crowd, praising the first round of voting and urging them to back him.
"We campaigned in a warm environment, and today we hug each other in a warm environment," he said. "This is our joint commitment, and we are moving forward together to the point of victory or to the point of final results -- either in the first round, [God willing], or the second round."
The outcome of the first round surprised many Afghans because Mr. Abdullah received votes from across the country, even in heavily Pashtun areas. Overall, the election garnered more interest from voters than the last presidential contest in 2009, with 50 percent more votes cast, and it was viewed as generally less fraud-ridden.
The argument by Mr. Abdullah's backers is that with Mr. Rassoul's support they have 55 percent of the votes cast nationwide, well above the 50 percent threshold required by the constitution -- so there is no need for a runoff. Mr. Abdullah's team also won the endorsement of another candidate, Gul Agha Shirzai, a former provincial governor who won just 1.6 percent of the vote.
However, the Afghan Constitution specifically requires a runoff between the two top vote-getters, not between coalitions the candidates form afterward.
As news was breaking of Mr. Abdullah and Mr. Rassoul's allegiance, a suicide bomber attacked an Afghan security forces convoy near a clinic in Kandahar, killing four civilians, according to provincial police.
A NATO convoy was nearby delivering aid packets but was not affected by the blast, he said.