With six weeks to go, Mr Sunak is around 24 points behind his rival among members. Polling shows they also believed the foreign secretary won both of the last debates.
For a campaign seemingly designed last year, Parliament’s richest MP appears to have skimped on ways to actually win over members beyond a slick video and snazzy font.
He’s going to lose if things stay as they are, and it’s not even going to be close.
Speaking to MPs supporting him, the mood has gone from excitement to genuine shock and a belief that it’s already done.
One told me: “He’s the only one who can beat Keir Starmer, but members are supporting a candidate they like more even though they’ll let Labour in. It’s over.”
Now after repeatedly stressing fiscal responsibility, Mr Sunak has promised to reduce tax in a bid to appeal to the membership.
His problem is, Ms Truss has already promised a slew of tax cuts, and it doesn’t look Prime Ministerial to say something mad and unsustainable unless you do it first.
The foreign secretary’s allies have already jumped on it. Business secretary Kwasi Kwarteng called it a “U-turn”, adding: “Being a grown up means that you can have tax cuts. I’m delighted to see that he’s come round to that view.”
Things are desperate and Mr Sunak needs to do something, anything, to take back control of this contest.
Any chance of doing so at the TalkTV debate was unfortunately cut short, and his list of opportunities grows thin.
He’s now set for a showdown with veteran journalist Andrew Neil, an interview Ms Truss has perhaps wisely avoided, just as Boris Johnson did.
If Mr Sunak is to have any chance of turning it around, he must remember winning isn’t about being responsible. It’s about selling a vision people like, no matter how unrealistic.