People are, however, getting very aerated about legitimacy. If the Coalition loses its majority, say Labour, then it will have no legitimacy and Cameron must resign. Ah, reply the Tories, but if the Tories win most votes and most seats, then a minority Labour administration, implicitly dependent on a separatist bloc of Scottish MPs would not have any legitimacy either. 'For God's sake,' reply various constitutional authorities, 'legitimacy is just numbers - any party that can get its Queen's Speech through is a legitimate one'.
The professors are obviously right in one sense. The actual law here is clear: the Prime Minister is the one who can command a majority in the Commons for his legislative programme. Equally, the law is clear that Cameron gets first go at trying:
Where an election does not result in an overall majority for a single party, the incumbent government remains in office unless and until the Prime Minister tenders his or her resignation and the Government’s resignation to the Sovereign. An incumbent government is entitled to wait until the new Parliament has met to see if it can command the confidence of the House of Commons, but is expected to resign if it becomes clear that it is unlikely to be able to command that confidence and there is a clear alternative.Talk of a "constitutional coup" is balls. Cameron is entitled, as Prime Minister, to try and make the numbers work for him. If they don't, he will resign. That's where the problems start. For Cameron to have tried that approach, the Tories would have to have significantly more MPs than Labour: say 20 more. For Labour to form an administration in those circumstances, where they will have lost disastrously in Scotland, and appreciably in England will look odd to most voters. As Phillip Collins says, while a minority Govt formed by the second largest party is unquestionably legal, legality and legitimacy are separate concepts.
It's worth remembering in this context that in 2010, the numbers for a 'league of losers' coalition between Labour, Lib Dems, and nationalists just about stacked up. A Government led by Gordon Brown, and supported by every non-Tory party in the Commons would have had a majority. That would have been a Government that was perfectly constitutionally permissible, but would have had a continuing crisis of legitimacy.
Let's spare a thought for the potential nightmare result: Tories largest party but unable to get over the line with Lib Dem/DUP support; Labour second but unable even with SNP to get to majority. The rules say that Cameron should resign if he can't command confidence of the House AND there is a clear alternative. What happens next? Tune in next week...