That's right - having gambled successfully on the result of the Scottish Independence vote he gambled again. In both cases we understand the pressure that was on him - however it is right to blame him. Ultimately he did not have to make that decision
David Cameron promised to honour the result of the referendum. This would always have been difficult (in the case of a leave vote) because his party was deeply split and he was never likely to get a very big majority indeed it was a surprise that he got a majority at all. And then he buggered...