John Bercow faces a cross-party attempt to oust him as Commons Speaker when the House sits for the first time since the General Election.
MPs unhappy with Mr Bercow's speakership are confident that they can force a vote on his future, in what would be an embarrassment for him less than a year since his election.
Speakers are usually re-appointed on the nod, without a formal Commons division, at the start of each parliament.
But Mr Bercow has attracted open criticism of his approach and his opponents are ready to shout "No" when the question that he resumes the chair is put this afternoon.
Only one MP is needed to oppose the motion in order to force a full vote.
Nadine Dorries, who is leading efforts to get rid of Mr Bercow, said: "It is going to happen, there will be enough." She claims that Labour MP Kate Hoey is rallying opposition to the Speaker on the Labour benches.
Ms Hoey, who was in Northern Ireland on Monday night, said she would try to force a division if she was back in Westminster in time. "If there is an opportunity to say 'no' I think the new parliament should have an opportunity to elect a new Speaker," she said.
However, even if there is a division, it is far from clear that Mr Bercow could lose the subsequent vote, although the plotters against him expect a large number of abstentions. Should he lose, there will be a secret ballot of MPs on Wednesday to elect a new Speaker.