The real reasoning behind it is two-fold: firstly, something has to be thrown towards the increasingly restive Tory grassroots, as well as the focus groups that keep reporting on the loathing for imm'igants and scroungers. Never mind that if the Euro goes down as is still possible there's likely to be an increase in both and they'll be very little we can do about it, and that the only place further cuts can be made in welfare is to pensioner's benefits, something has to be done. Second is the unrealistic promise made by the Conservatives in their manifesto, and somewhat carried into the coalition to reduce immigration from the hundreds of thousands a year to the tens of thousands, the clear implication being to return to the levels seen under the last Tory government before Labour "opened the floodgates". Numbers have instead stubbornly stuck around the 250,000 net increase level, despite the Tories repeatedly claiming that they're beginning to make progress.
To be fair to the Tories when they don't deserve it, this is a case of the cliched policy chicken of all three parties coming home to roost. At the last election all three failed to make the case for continued immigration, while at the same time defending what had gone before. No one suggested that if those who had come before had contributed so much, it was daft to say that it should now immediately cease, as that wasn't what the polls, focus groups and the tabloids were telling them. Instead of being honest, and suggesting that it was likely in the 21st century that there was little they could do to control immigration when there are 5 million Britons living abroad and the economic situation is as bad as it is, all gave the impression that the drawbridge was going to be raised. This wouldn't have been an easy thing to do, to say the least: it would have meant short-term unpopularity, and perhaps could have only been done after the election. Doing the opposite though, as all three leaders did, was to raise expectations that something would change, when they knew it was unlikely in the extreme. Disaffection, anger and unpopularity then await.
It hasn't quite ignited yet, probably because there's been so much else to quietly simmer about. All the more reason to make gestures like today's, which Theresa May made clear would do relatively little to get the numbers down. According to her Commons statement, 18% of the total is family migration, meaning that even if the entire route was closed down it wouldn't get the figures to anywhere near under 100,000. Ian Birrell makes the point that this goes dead against the Tory policy of making Britain the most family friendly country in Europe, having promised they would support families to stay together, even perhaps eventually recognising marriage in the tax system. Forcing up to 15,000 families a year to emigrate or live apart, as he writes, is "morally suspect" and even threatens the detoxification of the party.
That's a bit strong, both because the popularity of Osborne and Cameron has already slumped, and also due to how May's presentation of the measure of ensuring that the system can't be abused by scroungers rather than putting restrictions on love has mostly been swallowed whole. It does though highlight the coalition's rightwards drift: having started off with Ken Clarke's aim to reduce the prison population, we now have a new snooper's charter, secret "justice" and pointless grandstanding like "making clear" that Article 8 of the Human Rights Act is clarified, as if judges didn't already know and resent the implication that they bend over backwards to let foreign criminals stay here as long as they grow potted plants. What it does do is placate the Sun and Mail for all of a day, and at the moment, that seems to be enough.