While this is constitutionally correct, I don't think a reference to the constitution can settle the matter for two reasons:
1) There is also no constitutional reason why there shouldn't be an election, since calling one lies within the prerogative of the Prime Minister.
2) There is no constitutional requirement for a couple of conventions that have developed since Blair came to power. One is the idea that the legislature should be consulted in the event of Britain going to war. The other is that the electorate should be consulted by plebiscite on political changes that are considered fundamental constitutional changes, such as regional devolution.
It isn't only opponents of the war or devolution that could complain the manner in which both of these 'democratic consultations' were carried out was far from ideal. But the point is that our constitution is flexible enough to accommodate the development of conventions that appear to conform to democratic protocol - and at the same time it doesn't have the rigidity that allows it to be the final word on whether calling an election is appropriate.
Making a rare excursion into domestic electoral politics, Norm argues it wouldn't be - not so much on the basis of constitutional convention but rather on the grounds that there simply is no democratic need to do so. (I'm assuming everyone reading this understands that while the two may and do overlap, they are not the same thing.) And given this is the case, he argues an 'unnecessary' election would be seen as opportunistic by voters:
"The Labour Government has a mandate to govern that extends until the spring of 2010! Under the rules of this parliamentary democracy Gordon Brown needs no personal mandate of his own; the mandate belongs to his party. So the only conceivable reason for calling an election is to gain an electoral advantage - on the basis of polling predictions. This will be transparent to voters. What credible public justification could be offered for so unnecessarily premature a move?I think most people agree that the idea of governments having a mandate to carry out a raft of policies is a myth that doesn't bear too careful examination. But it shouldn't be dismissed completely, I think, for a couple of reasons.
If Brown does go ahead and call an election and it doesn't pay off, then he and his party will look - deservedly - sick. If it pays off, then it pays off. But it will do no credit to Brown, the Labour Party or British parliamentary democracy."
One is that while it isn't credible to claim that every action a government takes has the wind of the electorate's prior approval behind it, provided it was in the manifesto, I don't think voters perceive themselves as giving parties a 'doctor's mandate' to govern in any manner they see fit. The electorate would see abrupt reversals in major policy areas as something for which they didn't give their approval and could justifiably complain they weren't consulted.
Moreover, even if this were not so - surely a change in the doctor who has the mandate is something they might reasonably expect to be asked their opinion about sooner or later? I'm not sure it's good enough to say that it's the same party in government so the change of personnel at the top doesn't matter, still less that 'people knew it was going to happen anyway'.
Secondly, even if you found all this unconvincing, surely you would have to agree that politicians use the myth of the mandate regularly to justify their own actions, or to undermine the legitimacy of others when they're in opposition? You could argue then that a 'public justification' might be required of them for not holding an election sooner or later, since the logic they've used in the past would suggest they should. I seem to remember, for example, some opposition MPs claiming that Major had no 'mandate from the people'.
So I can't agree with Norm that the "only conceivable reason for calling an election is to gain an electoral advantage" but in any event, surely every government that has the scope to do so calls elections at a time when it is most advantageous to them? So where's the evidence that the electorate punish them for doing this? Whatever the reason, do people really resent being asked who they want to govern them because it's 'too early'? "How dare you ask us this - the mandate we gave you hasn't expired yet." Come off it. They didn't punish Margaret Thatcher for this; would they perceive a November election as more calculating of advantage than 1983?
Conclusion: why not have an election? I don't find any of the arguments against it very convincing. It's all academic anyway because the only one Brown and his crew will have been taking seriously is the "because you might not win it" one.