Boris Johnson supporters are threatening to send a protest bus to picket the Tory leadership hustings.
Conservative members will be invited to 12 campaign events in the six-week run-off as Liz Truss and Rishi Sunak battle it out to be the next Prime Minister.
But angry Johnson backers are campaigning to give members a say on whether they accept the PM's resignation.
Multi-millionaire tycoon Lord Cruddas, a former Tory Treasurer, is leading a push for a yes/no vote on whether Mr Johnson should go.
He said one idea was for a “Boris bus” to go to the hustings to protest the PM's resignation, which came after mass resignations threatened to collapse Mr Johnson's Government.
Lord Cruddas told the Telegraph's Chopper's Politics podcast: "That's a possibility. People are angry, they want to protest and members want to protest."
He went on: "We're a good campaign. We're about sticking up for the members. And so if the members want to campaign, that's up to them.
"We just got down to the final two. But it wouldn't surprise me if you don't see protests and a battle bus."
Angry Tories could also spoil their ballot papers by writing "none of the above", or even " Boris Johnson " on their voting slips, he suggested.
Asked what he would write on his ballot paper, the peer said: "I'll write Boris on it."
Lord Cruddas blasted the decision to oust Mr Johnson as "anti-democratic", adding: "The members of the Conservative Party are very angry. They have been undermined by the parliamentary party."
The long-time political donor has refused to hand over £500,000 of donations from himself to the party in anger at the PM's departure.
“I planned to donate a total of £500,000 this year but that is on hold and will not be paid unless the membership have a chance to vote on Boris being PM," he recently told the Sunday Times.
“I have no interest in Rishi who I deem to be not fit for high office due to his plotting and the orchestrated way he and others resigned to remove the PM."
Last year Boris Johnson overruled advice from the Appointments Commission to put Peter Cruddas in the Lords after he failed its vetting process.
Lord Cruddas, who founded CMC Markets, is a former Tory Treasurer who has given millions to the Conservatives, and also donated large sums to the Vote Leave campaign.
