But why didn't the PM answer himself?
Both parties’ interests lie in the Conservatives' campaign strategist sticking around. He can't win over the liberal voters the Tories need for victory.
Having previously enjoyed a double-digit advantage over the Tories, the party's lead has been reduced to single figures, far below the level needed to be confident of victory.
A Conservative majority remains unlikely and EU treaty change could take many years to come to fruition.
IDS will appear before the work and pensions select committee on 4 September to answer questions over his misrepresentation of welfare figures.
With a Conservative majority almost certainly out of reach, Cameron must redefine as victory something the Tories have tasted once before as defeat.
Five days after the government postponed the introduction of plain cigarette packaging, the Tories' campaign strategist remains the story.
The Tories' attempts to pin the blame for NHS failings on the former health secretary are both politically unwise and unmerited by the facts.
The measure proposed by the 40 Group of Tory MPs will do little to reduce the welfare bill, while further stigmatising an already marginalised group.
The decision to only provide help with childcare costs to those paying income tax means work will not pay for 900,000 families.