What a difference 24 hours make. On Thursday morning, after an unexpectedly powerful speech from Hilary Benn, the Labour leader Jeremy Corbyn was reeling. The look on his face as Benn was applauded - applauded! - in the Commons chamber said it all. Not a good day at the office.
Twenty four hours later, after a stonkingly good by-election victory in Oldham West and Royton, Mr Corbyn is entitled to turn on his critics: "Can't win elections? Too extreme? Really?" On a wet Thursday in December, after a parliamentary debate that showed the party's deep divisions in all their gory splendour, Labour actually increased its share of the vote, up 7.3% compared to the general election in May. A good day at the office.
Lesson One: don't believe what you read in the papers. But Lesson Two: take the long view. Labour has not suddenly become a lean, mean election machine, simply because it won a by-election in what should always have been a rock-solid seat. The party's civil war is only just beginning, and just like the war in Syria, it will be long, messy and bloody.
It is tempting to quote Macbeth and see politics as little more than "a tale told by an idiot, full of sound and fury signifying nothing." Tempting, but wrong. The past few days have signified a great deal for both the UK's main political parties. They have probably signified rather less, however, for the people of Syria, ostensibly at the heart of this week's debates.
For the prime minister, Wednesday night's Commons vote authorising RAF action against IS targets in Syria as well as in Iraq marked the successful conclusion to a two-year campaign to reverse the humiliation of his defeat in 2013 when Labour under Ed Miliband refused to back his proposal to send the RAF into action against President Assad. As the Financial Times put it, this week's vote marked "a return to the world stage by a prime minister accused of presiding over a 'deeply worrying' strategic shrinkage."
For Mr Corbyn, the debate brutally demonstrated his tenuous hold over his parliamentary colleagues, and the toxic nature of some of the key relationships inside his party. The Oldham result will encourage his supporters to ratchet up their pressure on unconvinced Labour MPs: "You say we're unelectable under Corbyn? What about Oldham?" The result will do nothing to heal the party rifts.
So what does it all mean for Syria? In his Commons speech last Wednesday, Mr Corbyn said: "Yet more bombing in Syria will kill innocent civilians - of that there's no doubt - and turn many more Syrians into refugees." It is impossible to disagree: bombs kill people, and not only the people against whom they are aimed, yet it is worth examining the record.
According to the Ministry of Defence, "in more than a year of strikes against Daesh (IS) targets in Iraq, there have been no reports of civilian casualties resulting from UK air operations. RAF Tornado and Reaper aircraft have flown a total of 1,632 combat missions and have carried out more than 380 successful strikes in Iraq."
Maybe. Chris Woods of the independent monitoring organisation airwars.org estimates that more than 360 civilians have been killed in Iraq by coalition air attacks over the past year, but it is impossible to calculate how many, if any, of them were a result of UK action. Professor Lawrence Freedman, Emeritus Professor of War Studies at King's College, London, is prepared to accept the MoD claim but warns that they are "not a sure guide" to likely consequences in Syria.
According to US press reports, in Iraq several hundred Sunni tribesmen, trained by US soldiers and backed by US air strikes, are expected to join Iraqi army troops imminently to launch an assault on the IS-held city of Ramadi. If they do - and if they succeed in dislodging IS - it will be heralded as an example of how air strikes can help in the battle of attrition against IS.
There is, of course, one big difference between Iraq and Syria. In Iraq, foreign intervention forces work side-by-side (up to a point, anyway) with the national army. In Syria, at least for now, similar cooperation with Assad's army is inconceivable. It will make the task in Syria even harder than it is in Iraq. But, in my view, that doesn't mean it's not even worth trying.
On their own, a few more air strikes from RAF Tornados and Reaper drones will not turn the tide. But if UK participation in the Syria air campaign gives the British more clout at the negotiating table, together with such key players as Russia, Iran, Turkey and Saudi Arabia, this week's Commons vote will not have been in vain.