Respect candidate George Galloway has been advised to stay away from his home after receiving a death threat.
Both candidates have been intimidated
At a hustings meeting on Wednesday Mr Galloway and his Labour opponent Oona King stood together to plead for less negative campaigning.
Both candidates, contesting the Bethnal Green and Bow constituency, have required police protection.
Mr Galloway was allegedly "threatened with death" by Islamist extremists at a meeting on Tuesday evening.
The 40-strong mob apparently locked the door and denounced him as a "false prophet" and declared the sentence for this was "death".
Mr Galloway said: "It was a very frightening incident caused by a tiny, unrepresentative group of very extreme fundamentalists who believe that elections are a crime against Islam."
On Wednesday Miss King, who has been criticised for supporting the Iraq war, required police protection to separate her from opponents.
Her car tyres were slashed and she was pelted with eggs last weekend.
And last week eggs and vegetables were thrown at her when she attended a memorial to Jewish war dead.
Miss King said: "I utterly condemn any attacks on George Galloway, or any other politician, and indeed just the general atmosphere of intimidation.
"I have to say it has not been helped by some of the language used by Respect. Extremism breeds extremism."
Mr Galloway and Miss King appeared together amid tight security at a meeting at the University of London on Wednesday evening.
Miss King told the audience that Mr Galloway had agreed to a meeting with election organisers and other candidates to try to "take some of the heat and vitriol out of this campaign".
Mr Galloway said: "Can I take this opportunity to express to Oona King how sorry I am for what has happened to her in this campaign and to welcome her call this evening for all the parties to talk with the police about how we can take some of the negative atmosphere out of this campaign and how we can see democracy prevail."
Respect is a coalition that grew out of socialist and trade union opposition to the Iraq war.