Sky News report
It's not looking good for May heading into tomorrow's vote. This is the time when you need your whip the most.
His resignation letter said the current deal doesn't respect the referendum result because it would leave the UK overly tied to the EU. Johnson said he was resigning because he couldn't whip the votes on a deal he couldn't support himself.
Ok, fine, but you wait until the day before the vote to do it? That seems like a stab in the back.