Nick Clegg may publicly insist that he is neutral between the Tories and Labour but today's PMQs (at which he deputised for the absent Cameron) was a reminder of why it is so hard to imagine him working with the opposition if there is another hung parliament in 2015. Such was the ferocity with which Clegg tore into Harriet Harman that, by the end, his Conservative bête noire Peter Bone declared that he was "turning into a Tory".
Taking his script straight from CCHQ, he attacked Labour's energy price freeze as a "con", "economically illiterate" and "a fantasy". This was followed by a series of Cameron-esque blasts at the party's trade union "bosses" and "paymasters", and an unqualified defence of the bedroom tax (which his party's conference voted against) on the grounds that it was merely a continuation of the policy introduced by the last Labour government in the private sector. With Tory MPs cheering him on, he declared that Labour wasn't even an "opposition-in-waiting", let alone "a government-in-waiting", a line that shows why a Clegg-Miliband coalition seems increasingly implausible.
Both Labour and Lib Dem MPs attempted to lure Clegg away from his Tory masters, with Lucy Powell questioning him on Cameron's marriage tax break plans (which his party opposes) and Charles Kennedy asking him whether he welcomed the fact that Cameron was now a loyal supporter of Britain's EU membership (on account of the pro-European policies pursued by the government). But Clegg failed to rise to the bait, merely praising Kennedy for his "mischievous wit and wisdom" and, on the marriage tax allowance, remarking that there were acknowledged "differences" within the coalition.
There were jeers from both sides when he rather hyperbolically declared that "without the Liberal Democrats, there wouldn't be a recovery", a preview of what will be his main general election message. But after his blitzkrieg against Labour, the Tories were content to let it pass. Clegg's challenge is to ensure that his party wins its share of credit for the return of growth, while doing enough to differentiate itself from the Tories. Rarely has he failed more in this balancing act than today.