This campaign has already been marked by bitter disputes and astonishingly personal attacks.
But the fact that dozens of Conservative MPs have been willing to sign up to criticise the chancellor so very publicly today illustrates that some bonds have been broken beyond repair - and that the conduct of the referendum has damaged George Osborne's reputation among his colleagues.
Vote Leave isn't just edging towards presenting an alternative view of Tory government, but a coup in waiting.
It is certainly bold, if not extreme, for a chancellor to sketch out a hypothetical budget in this way - with warnings of cuts and tax rises.
But the motivation is clear - with the referendum, and careers on the line, the Remain camp still believes their best hope is to shout about the potential downsides to the economy we'd all feel if we vote to leave.
As one insider put it they are going with the grain of public anxiety - with the economic consensus that leaving is a huge gamble with the country's prosperity on their side.
But shout too loudly, and the message might simply deafen, rather than persuade.
"Smart guy, stupid move" - one of the kindest descriptions by Leave MPs of George Osborne's Brexit Budget move.