Mike Nesbitt has long been accused – even by some in his own party – of cosying up to Peter Robinson.
Cartoons have depicted the former TV anchorman as a poodle already collared by the more wily First Minister.
And so, at least in the months after Nesbitt succeeded Tom Elliott as leader– who only lasted a year in office – it seemed Nesbitt appeared to play second fiddle in the moves which led to him and Robinson lowering the temperature of the Union flag protests by setting up the Unionist Forum.
And he took a considerable gamble in agreeing to run a joint candidate with the DUP in the by-election battle for the Mid-Ulster House of Commons seat vacated by Martin McGuinness (even though it was a shoo-in for Francie Molloy).
However, Nesbitt always argued that while he would work with his main rivals in areas of mutual interest, he and Robinson were not exactly bosom buddies.
And he knows the key to survival for his party is putting red, white and blue water between the UUP and DUP.
Their first key division was when Nesbitt became the most prominent figure involved in the campaign, also including the TUV's Jim Allister, that forced the DUP's U-turn on the proposed peace and reconciliation centre at the Maze.
But Nesbitt has also proved a considerable thorn in the side of the First Minister, as chair of the committee which monitors his and the Deputy First Minister's department.
And now the gloves are off after Nesbitt launched a no-holds-barred attack, lighting the blue touch-paper for a full frontal assault on the DUP.