The coalition fractures start to show

Prime Minister David Cameron committed something of an historical gaffe this week when he referred to Britain having been the Americans' "junior partner" in 1940 in the war against Hitler.

Given that the US did not even join the war until 1941, it was not even historically accurate, quite apart from the, probably unintended, slight on our own WW2 heroes.

But while Mr Cameron was busy making friends across the pond, his own 'junior partner' was committing a possibly more serious gaffe in regard to a more recent conflict.

Standing in at PMQs, deputy premier Nick Clegg allowed himself to be goaded by Labour's Jack Straw into declaring the 2003 invasion of Iraq "illegal."

The comment was interesting on both a personal and a political level. It demonstrated that, for all his polished performances in the TV election debates, Mr Clegg hasn't yet quite made the transition from leader of a protest party to statesman.

While many voters will applaud his honesty in speaking from the heart, ministers sometimes have to be more circumspect.

More broadly, the comment also highlighted the fact that the Tories and the Liberal Democrats are very different parties, one instinctively pro-establishment, the other instinctively anti.

As we come to what is generally considered to be the end of the political year, the talk at Westminster is inevitably that the coalition is showing its first signs of fracture.

If the truth be told, the tensions were there from the start, but they really only began to come to a head once the scale of George Osborne's Budget cuts became clear.

If there were protests on the Lib Dem side about that, they were then more than matched by the mutterings on the Tory benches following the announcement of the electoral reform referendum to be held next May.

Then, this week, came Mr Clegg's PMQs outburst and a separate row over the Lib Dems' proposed graduate tax to pay for higher education, which the Tories have now turned their backs on.

Still to come in the autumn is a party conference season in which I expect to hear Lib Dem activists sounding-off loudly about the Tories' plans to reform education and the NHS.

With an election theoretically five years off, no-one is currently paying too much attention to opinion polls, but they nevertheless paint an intriguing picture of how the public mood has shifted since 6 May.

Leaderless Labour are up an average five percentage points for the loss of Gordon Brown, which tells its own story of what might have happened had someone else been leading them on election day.

Meanwhile Mr Cameron's Tories are up around eight percentage points at 44pc, while Mr Clegg's Lib Dems have slumped to around 13pc.

The worrying conclusion here for the Lib Dems is that while the public seems to generally approve of what the government is doing, it is currently only benefiting the Tories rather than them.

One of the most prescient questions of the week was posed by the blogger Henry G Manson, writing on the excellent PoliticalBetting.com website.

In a neat reworking of the title of an old club anthem from the late 1980s, he asked: "Clegg: How low can he go?"

Henry's point was that there has to come a point beyond which Lib Dem MPs and activists will not allow the party's support to slump before they are finally moved to act.

I suspect that this is a question which will not only help shape the politics of the next 12 months, but one which may ultimately determine the fate of the government.