KABUL, Afghanistan – Afghanistan’s first presidential campaign has picked up markedly in its final days, with the 17 candidates standing against President Karzai now whizzing around the country to drum up support.

Kabul is plastered with posters while outside the capital candidates have been traveling from city to city holding small rallies to woo voters outside their ethnic group.

In Qarabagh, a small town 50 miles north of Kabul, young men appeared enthusiastic about voting for the first time. In a high-school physics class, young voters named at least six different candidates they would vote for, though many of the 17 opposition hopefuls are barely known outside Kabul.

Saturday’s election is crucial for the long-term stabilization of Afghanistan, but in the short term important to President Bush’s re-election campaign. As Senator Kerry inches up the polls and as the scheduled January elections in Iraq look increasingly doubtful, Mr. Bush has touted the Afghan elections as a foreign policy success for his administration – even though they still have to take place.

Contrary to previous estimates by diplomats and Afghan government officials that Mr. Karzai would easily get far more than the 50% required to avoid a second run-off election, it appears that at least three leading opposition candidates are doing better than expected. Unlike Mr. Karzai, none of them is a national leader, but they are relying on blocks of votes from their own ethnic groups, which could intensify the still deep divisions in the country.

Mr. Karzai, who is expected to sweep the south where his fellow Pathans live, has to ensure that he receives votes from smaller ethnic groups in the north and west in order to emerge as both a national leader and a healer of ethnic divisions.

There is little doubt that Mr. Karzai will win, but the question now is by how much. With no polls available, everything in Afghanistan is a guess, but some diplomats and senior government officials predict that Younus Qanooni, the Tajik leader from the Panjshir valley, a former education minister in the Karzai cabinet, could receive as much as 25% of the vote – the majority from Tajiks.

With campaigning ending on Thursday, Mohammed Mohaqeq, a leader of the Shia Hazaras from central Afghanistan appears to be picking up the majority of Hazara votes which could be 10% or more of total voters while General Rashid Dostum, the Uzbek leader, is claiming support from a majority of Uzbeks in the north.

These ethnic blocks plus the few votes that the other – largely unknown – candidates receive could prove problematic.

“The danger is that if Karzai receives just under or just over 50%, the losers could unite to demand a run-off election or, even worse, denounce the elections as fraudulent,” said a senior diplomat.

Opposition candidates are now discussing whether they could narrow the field by presenting just one to three candidates to oppose Mr. Karzai, rather than 17, thereby increasing their chances of doing even better.

Mr. Karzai’s supporters are adamant that he will achieve a comfortable majority, which will see off any further challenge and establish the credibility of the election.

“I am sure Karzai will receive at least 65% of the vote,” said the interior minister, Ali Jalali. In the weeks leading up to the elections, American and European diplomats and leading Afghans on both sides of the divide were desperately trying to cement a deal between Mr. Karzai and Mr. Qanooni, under which Mr. Qanooni would step down as a candidate and receive several ministerial slots for his group in return.

That deal fell through as hardliners on both sides insisted that their leaders go it alone. Many Afghans said a deal would have boosted the suspicions of a skeptical Afghan public that the poll was being stage-managed.

Separately, Taliban and Al Qaeda terrorists have failed to launch a serious attack on Kabul or the candidates in the presidential campaign, but not for want of trying.

“Since October 1, we have caught more than 100 Taliban, some based in Afghanistan, others trying to cross from Pakistan,” said the Afghan interior minister, Ali Jalali. “We have also uncovered more than a dozen plots to use explosives in Kabul.”

On Sunday security forces stopped a lorry laden with explosives and primed with detonators outside Kabul. A few days earlier, in a raid on a house, they found a cache of suicide explosive belts, a standard Al Qaeda weapon.