By Mirwais Harooni and Katharine Houreld
KABUL, March 16 (Reuters) - Afghanistan's former defence minister became on Sunday the second candidate to drop out of a presidential election race, with his departure possibly helping consolidate support for a candidate favoured by outgoing President Hamid Karzai.
Rahim Wardak was not considered a front runner in the April 5 election and he did not throw his support behind any other candidate.
"We can confirm that Rahim Wardak resigned from elections as a presidential candidate and will not run," his spokesman, Sayed Baqer Kazimi, told Reuters.
"It was his personal decision. He will not support any other candidates. If there are any changes we will inform the people of Afghanistan."
Wardak was one of 10 candidates hoping to replace Karzai, who has served two terms and can not stand again.
The election is seen as a crucial step in building stability in Afghanistan in the same year that most foreign troops are due to leave after 13 years of inconclusive war against a stubborn Taliban insurgency.
Karzai's brother, Qayum Karzai, announced he was dropping out of the race this month and threw his support behind former foreign minister Zalmay Rassoul. That was widely interpreted as meaning Rassoul had Karzai's backing, although the president has not officially given his backing to any candidate.
Of the nine candidates still in the race, the three front runners are generally sees as Rassoul, outspoken former finance minister Ashraf Ghani, and Abdullah Abdullah, an eye surgeon who became the top aide to an anti-Taliban resistance fighter, and who is also a former foreign minister.
All the candidates are ethnic Pashtun, Afghanistan's largest ethnic group, except for Abdullah, who has a Pashtun father and ethnic Tajik mother, and draws support largely from the Tajik minority.
Wardak is also Pashtun, as is Karzai, so his support is likely to go to another Pashtun candidate.
With many Afghan voting along ethnic lines and with the Pashtun community an estimated 45 percent of the population, it is generally believed that a Pashtun candidate will win.
If no candidate gets 50 percent of the vote, a second round will have to be held, as happened in the last presidential election in 2009 which was marred by accusations of vote fraud.
Abdullah, Karzai's main challenger in 2009, said in a recent interview Karzai had flooded the race with Pashtun candidates, some of whom would drop out at strategic times, leaving Pashtun support to consolidate around his favoured candidate.
"Right from the beginning, President Karzai has designed it so he could manoeuvre it, in order to stay relevant to the situation mainly, but also to influence the future course of action," Abdullah said.
Fraud is not the only potential problem. The Taliban have threatened to kill anyone taking part in the election, which they describe as a "sham" being manipulated by the United States.
At least eight members of various campaigns have been killed and there have been five attacks, including a kidnapping, since campaigning began, according to the National Democratic Institute, which is monitoring the vote. (Editing by Robert Birsel)