Supporters of the former transport minister lobbied a meeting of London Tories in an effort to rescue his campaign for the candidacy.
Mr Norris's chances received a boost when Michael Ancram, the party chairman, made clear the leadership would not oppose such a move. His comments came as senior Tories claimed the party was in danger of losing the only man who could beat Ken Livingstone or Frank Dobson.
Mr Norris was dropped by the Conservatives' 12-strong selection panel at the weekend. The panel decided to bar him after four senior party officials from his former Epping Forest constituency claimed they would have dropped him as MP because of his extra-marital affairs if he had not quit.
But Tory activists across London rallied to his defence yesterday and said they would overturn the decision at the meeting of the party's electoral college last night.
The electoral college, made up of the selection panel and representatives of the 74 London constituencies, met to interview the four remaining candidates, Andrew Boff, Baroness Miller, Baroness Hanham and Mark Kotecha. Norris supporters were expected to propose a motion to allow the shortlist to be increased to five, in effect allowing Mr Norris to take part in a hustings meeting tomorrow.
The hustings will narrow the field to two candidates before a one member, one vote ballot next month among the capital's 30,000 party members.
Mr Norris said yesterday that "dozens" of local party chairmen across London had telephoned to offer their support. His camp estimated that 40 out of the 74 local parties had pledged their backing.
"There is a real risk for the Tory party of forgetting what politics is about. Politics is about winning," Mr Norris said.
However, the flamboyant former MP upset several Conservative Central Office insiders when he made a savage attack on the "monstrous regiment" of women in his old constituency in an article in yesterday's London Evening Standard.
He singled out Di Collins, constituency chairman when he was MP and mother of the Tory party vice-chairman Tim Collins. He said she had tried to make life difficult for him following press disclosures about his extra- marital affairs. "She herself had been through a messy divorce and had seen her husband go off with a younger woman. Hardly surprising whose side she would take in my case," he said.
Earlier, Mr Ancram made clear that the constituency associations in London had to make the choice for themselves. "It's open to [last night's] meeting to consider what motions it deems to be appropriate and to take decisions on them," said Mr Ancram. "That is what democracy is about. And I'm sure [it] will be a democratic meeting."
But Mr Ancram declined to give a view on Mr Norris's merits, repeating William Hague's stance that he wanted as wide a field as possible.
"I have made it clear all along that who is in the race and who is eventually selected ultimately is a matter for the members in London, and I made it very clear that I wasn't going to express an opinion on that," he said.