Why would a Conservative Party want the SNP to succeed at the expense of Labour? This is because, barring a major campaign earthquake, it is now impossible for Cameron to get the keys to Downing Street after May 7th. Cameron knows that his best bet now is for the Conservatives to be the largest party, even if they cannot form a government.
So Cameron needs the earthquake to happen – and soon – because, with even the most generous prediction, Cameron is already “locked out” of No 10.
Even if the Lib Dems managed to do far better than every poll predicts – and most are suggesting they’ll get around 26, Cameron cannot make the 323 seats needed to form another coalition or govern as a minority. If the Lib Dem exceeded expectations and won 28 of their targets, that would still leave Cameron needing 295. That’s around a full five point lead for the Conservatives over Labour. So far, in this election, there’s just no sign of it happening. (Don’t forget, Ukip could win as many as four seats – but it is inconceivable the Lib Dems would form a coalition that contained such a euro-sceptic party).
On the other hand, the numbers for Miliband work much better, giving him far more options to broker a deal, formal or otherwise. With the SNP on anything between 40 and 55, and the Lib Dems gaining just 20 seats, for example, Miliband can govern even if he just scrapes 270 seats.
So the problem for Cameron is also the strategy of a man leading a party he knows can’t win. If he “talks up” the SNP it doesn’t really alter Labour’s chances of forming the government. But, what it might – just might – do is make the Conservatives the largest party, albeit unable to form a government. This would give the largely Tory-supporting press a field day, allowing them to question the legitimacy of Miliband as Prime Minister. What it won’t do, however, is hand him the election.