In recent weeks Ed Miliband has lost support, lost momentum and today he almost lost his voice.
"If he gets a doctors appointment I do hope he doesn't forget it," joked Cameron in response to a spectacularly unwell sounding Labour leader.
The battering Miliband has taken in recent weeks over his failure to remember his conference speech has clearly taken its toll on him both politically and physically.
Today he looked like a man desperately counting down the minutes until he could return to bed. He may technically still have been one of Nick Clegg's "alarm clock heroes" but he certainly didn't look like it.
"I wouldn't miss this meeting with the prime minister for the world," he insisted in what must be the least believable statement he has ever made.
"He's obviously noticed that I lost a couple of paragraphs in my speech," he continued bravely.
"Well I noticed that he's lost a couple of members of parliament."
If the Labour leader was hoping for deafening cheers from his party benches for this, he will have been disappointed.
Support for Miliband among his MPs has always been far from healthy, but recent events have left it anaemic to the point of full scale angina.
Yet grumblings about his leadership have never completely erupted, largely because of his repeated knack to pull out good performances when he needs them most.
Today turned out to be yet another one of those occasions. His revelation of a quote from the government's welfare minister Lord Freud describing disabled people as "not worth" the minimum wage risks being hugely damaging for the Tories.
Claims that a government minister even considered allowing disabled people to be paid as little as £2 an hour plays into the perception that the Conservative party are only concerned with looking after the rich and the powerful.
"I don't need lectures from anyone about looking after disabled people," Cameron barked desperately in what is increasingly now his standard response to any criticism on his health or welfare policies.
"I don't want to hear any more of that. Instead of casting aspersions, he should get back to talking about the economy."
It's no surprise that Cameron didn't want to hear about it. The biggest obstacle to a Conservative majority at the next election remains this deep and widespread negative perception of the party.
Miliband today gave a highly useful reminder to his party, that whatever his own apparent political and physical weaknesses, the political weakness of the Conservative party remains far bigger
And while all of the focus in the following weeks will be on the rise of Ukip, it is this basic negative perception of the Tories, rather than anything Nigel Farage can ever say or do, that remains the biggest obstacle to David Cameron clinging to power next year.
Both parties may be on their sick beds, but it's Cameron's condition that still looks most difficult to treat.