The two victims were gunned down Saturday in the western city of Herat while working for Abdullah Abdullah, one of the 11 candidates seeking to replace outgoing President Hamid Karzai in the April 5 voting.
The United Nations condemned the attack, which was likely the work of Taliban militants who have rejected the elections and have threatened to go on the attack.
Security has been a major concern for the government and the candidates, the BBC said Sunday. Each candidate has been provided with bodyguards and armored vehicles.
The BBC said political observers doubt Abdullah or any of the other candidates will win enough votes in April to claim victory outright, which means another round of voting in the summer.