When Malaysia Airlines flight MH17 was shot down over eastern Ukraine last month, public opinion towards Russia shifted drastically.
Before the crash most voters thought the Russia-Ukraine conflict was not a matter for the UK and the West. That changed after MH17. Voters wanted to impose sanctions, freeze Russian assets in foreign countries and even expel Russia from the G8.
Something similar is now happening over Iraq. A week of atrocities have hardened our attitude towards ISIS/IS – the "Islamic State" that has swept across Syria and Iraq and created its own independent caliphate.
Last September, nearly twice as many voters opposed than supported the US carrying out unilateral "missile attacks against Syria". Even more voters were glad the British avoided taking "any part in military action".
But people have responded very differently this week. In September, unilateral US air strikes faced twice as much opposition as support. Now voters have expressed the opposite view, and a majority of them support such strikes.
Similarly, the public is split on whether the RAF should take part. 37 per cent support the idea; 36 per cent oppose it. But in September 74 per cent of voters were glad MPs voted against Cameron’s call for conflict, and just 12 per cent disapproved.
This could be further evidence that public opinion changes when atrocities are committed and reported.
Or it may just be because of the way the question was phrased.
Last September YouGov asked a curt question that just asked about "Syria", and assumed voters knew the threat Assad’s government posed to the region. This time they accompanied their questions by asking whether US strikes were justified "to prevent the killing of religious minorities and to protect American personnel in the region".
By loading the question, they may have triggered a response. Most voters are probably unaware of ISIS’s actions.
When the MH17 crash was plastered over every paper and news site in the country, only a minority of voters "noticed" the story. Even fewer have registered the debate over "Iraq airstrikes".
Data from YouGov-Cambridge shows just 26 per cent of voters have picked up on it. It may be the most noticed story of the week, and the only thing many people are talking about, but three-quarters of the electorate still appear to be oblivious to it.