Several hopefuls vying to replace British Prime Minister Theresa May turned their fire on favorite Boris Johnson on Sunday, questioning his pledge to leave the European Union by the end of October no matter what.

With former London Mayor and foreign minister Johnson keeping a low profile, the other candidates have targeted the air waves to present their cases to lead the governing Conservative Party. But the question always returns to "Boris.

At a Channel 4 debate, his absence was marked by an empty lectern. That left the five other candidates to argue over which man was best placed to deliver Brexit in testy exchanges International Development Minister Rory Stewart described as a competition of "machismo.