It was Boris Johnson who actually won his first PMQs – and Corbyn is now on the back foot. This is why

Jeremy Corbyn could have given Boris Johnson a hard time at his first Prime Minister’s Questions. He asked tough questions about the consequences of a no-deal Brexit, and the prime minister conspicuously failed to answer.

But it was Johnson who actually won the exchanges easily because he challenged Corbyn on whether he wanted an election on 15 October – “or is he frit?” Johnson knows that the Labour leader wants an election but is being held back by his MPs, who are urging him to make life hard for the prime minister by refusing to vote for it.

Johnson returned to the theme repeatedly, calling Corbyn a “chlorinated chicken”, and was unexpectedly supported by Ian Blackford of the Scottish National Party, who quoted the opinion polls in Scotland and said: “If he wants an election, enable the bill and bring it on.”

This is not what most Labour MPs want to hear. They want to push the date of the election to after 31 October. Once the “rebel alliance” bill to block a no-deal Brexit has been put on the statute book, that would force the prime minister to agree an Article 50 extension.

That would present Johnson with an impossible choice: he would have to ask for a Brexit extension, destroying his credibility with Leave voters, or he would have to resign.

But I suspect that Corbyn’s calculation is different. He does not want Labour to be the “block Brexit” party, and he is confident of his ability to fight and win an election. So the leader of the opposition faces a huge decision.

He is likely to play for time tonight. The bill to stop a no-deal Brexit is likely to be passed by the Commons, at which point Boris Johnson could ask MPs to vote for an early election.

He has already tabled the motion under the Fixed-term Parliaments Act, but Corbyn says he won’t vote for it until the Benn bill goes through the House of Lords and becomes law.

So there is talk of an amendment to the motion being tabled by opposition parties, to make it clear that the Benn bill, which is designed to block a no-deal Brexit, has to be on the statute book first.

An amendment would nullify the motion. The Fixed-term Parliaments Act specifies the motion that must be voted through by a two-thirds majority: “That there shall be an early parliamentary general election.” If it is amended, the motion will be ineffective, but the amendment could be an important statement of intent.

If an amendment is passed tonight, then, the election will be on hold until the drama in the House of Lords is resolved. If the bill passes the upper house, possibly sitting on Saturday and Sunday, and receives the royal assent, the Commons could vote on Monday for an election on 15 October.

What will happen in the Lords? Peers quite enjoy the obscurity of their procedures. But my secondhand understanding is that the overwhelming anti-no-deal majority in the House of Lords will find a way to force the bill on to the statute book.

Then, on Monday, Corbyn will have to decide. The prime minister gave the game away during Prime Minister’s Questions, declaring at one point, “I want to have an election,” before he corrected himself: “I’m willing to have an election.”

Corbyn and the SNP want one too, but Labour MPs do not. It is now up to Corbyn to decide.