Why the outcome of the Commons vote on Syria is difficult to predict

It wouldn’t take long to describe parliamentary rebellions on British military action so far this parliament. There have only been four Coalition revolts, over three issues: continued British military involvement in Afghanistan in September 2010; whether or not to support UN Security Council Resolution 1973 (on Libya) in March 2011; and the wisdom or otherwise of ruling out military action against Iran in February 2012. Two of these three were debated under the auspices of the Backbench Business Committee, with Libya debated on the basis of a substantive Government motion. But the largest of these rebellions involved just four Conservative MPs and one Lib Dem, and in total across all three issues, just eight Coalition MPs have broken ranks on matters of war and peace, six Conservatives and two Liberal Democrats. So we can be confident that whatever happens tonight we will be able to say that it is the largest rebellion of its type during this Parliament.

The crucial difference with these votes and tonight’s is that they all saw the Labour frontbench support the government, as Her Majesty’s Official Opposition have in every other vote on military action since Suez in 1956. That the Government cannot rely on Labour support tonight is one reason why the outcome of the votes is so uncertain.

But it is only half of the explanation. The other half is the potential scale of backbench rebellion on the government side. This is a government with a de facto majority of around 80; even without opposition support it should not be in this position. Its difficulties are emphatically not a result of being a coalition. Whilst there will be some Lib Dem opponents, this is not a vote like that over parliamentary boundaries where the Lib Dems will defect en masse. The government’s problems are as much with Conservative backbench opponents, of whom there are said to be around 70.

This is just the latest piece of evidence of the steady rise of backbench independence, which we have been tracking over the last decade or more. It did not begin in 2010 – there were plenty of signs of it in both the 2001 and 2005 Parliaments – but there has been a further step change up in the levels of independence being displayed by MPs since the last election. This is a parliament that has seen MPs vote to amend their own government’s Queen’s Speech. Now they are willing to do the same to its foreign policy. This is parliamentary influence, for good or ill.

That said, we are equally confident that today’s rebellions will not top the record set by the Iraq revolts of 2003. Those are the largest rebellions by government MPs of any party, on any subject, since modern British politics began. The largest saw 139 Labour MPs vote against their party’s whip. But note that they did not start at 139. The first three rebellions over Iraq numbered 56, 30, and 44 respectively, only rising over 100 in votes in February and then March 2003 on the eve of war. Those early votes saw plenty of MPs express their unhappiness with the idea of military action without voting against their whip. Given that today’s vote is explicitly not one to authorise military action, we expect the same today, with MPs uneasy or unhappy taking the opportunity to make it clear how unhappy they are without actually voting against their party.

Will the government lose? Bluntly: they shouldn’t. The fact that this is not a vote to authorise conflict will be enough to placate some government MPs, even some with serious reservations. Then there is the fact that there are two votes tonight, one on a Labour amendment, one on the government’s own motion. This gives the whips some room for manoeuvre, with some MPs rebelling over the government motion, others over Labour’s amendment, but with each individual revolt smaller than the total number of rebels. Plus, if the issue becomes partisan – as it appears to be doing – that too will make some Conservative MPs uneasy about doing anything to help the opposition. But no one would put much money on a government victory, given events thus far this Parliament.

And if they do lose? When was the last time that happened? That is, as they say, a very good question. We struggle to find a vote lost by the government on military action any time in the last 100 years. For all that people go on about Norway in 1940 or Suez in 1956, the government won both of those votes. The former was enough to bring down a Prime Minister, but the government did still win the vote. We cannot find a comparable vote lost by a government, although our knowledge of the mid-nineteenth century isn’t what it was…

Iraq aside, most recent rebellions over military foreign policy, especially on the government side, have been small. Rebellions on the Iraq bombing of 1998 were small (just 22 Government MPs); ditto for Kosovo in 1999 (13) and Afghanistan in 2001 (11). There were some half-decent sized-rebellions amongst Opposition MPs against the first Iraq war in 1990-91, but not amongst government MPs. Iraq is very much the exception.

We suspect tonight’s rebellion will surpass these, but fall short of the 139 Iraq rebels. So perhaps the key remaining benchmark is with the vote in 1940, which brought down Neville Chamberlain, when 33 Conservative MPs voted against the Government, together with at least 60 who abstained. If tonight’s rebellion is of that magnitude, the vote will be very tight indeed.

Philip Cowley and Mark Stuart