A hashtag insulting presidential candidate Abdul Fattah al-Sisi has been circulating widely on social media in Egypt.
The hashtag, which translates as "vote for the pimp", has been tweeted hundreds of thousands of times.
Mr Sisi deposed Egypt's Islamist president, Mohammed Morsi, last July, after mass protests.
Earlier this week, he resigned as head of the armed forces and defence minister to stand for president.
He is widely believed to be the strongest contender in the May 26-27 vote given his popularity and the lack of any serious rivals.
Graffiti of the pimp hashtag has appeared on the streets of Cairo, below pictures of Mr Sisi's face.
The hashtag has prompted the creation of a number of counter hashtags in support of the former army chief, which were re-tweeted by his followers.
The BBC's Sebastian Usher says the media in Egypt has been muzzled and the Muslim Brotherhood outlawed under Mr Sisi's authority.
But there is one powerful and very Egyptian challenge he still faces - mockery.
One Egyptian blogger known under the alias "The Big Pharaoh", told the BBC that Mr Sisi's opponents were forced to used the hashtag due to the recent crackdown on demonstrations.
The social network, he said, was "the only arena where they can express their opposition, because now it is extremely hard to do demonstrations in Egypt with all the police crackdowns".
Mr Sisi's opponents hold him responsible for what human rights groups say are widespread abuses, and fear he wants a return to authoritarianism.
His supporters, however, view him as a saviour who can the end the political turmoil dogging Egypt since 2011 when a popular uprising ended Hosni Mubarak's three decades of one-man rule.
The crackdown on the Muslim Brotherhood has left more than 1,000 people dead and seen some 16,000 others detained since Mr Morsi was ousted in July 2013.
CORRECTION: An earlier version of this story incorrectly reported that the anti-Sisi hashtag had drawn a threat of arrest by the Egyptian authorities.