Labour tribalists and the media would immediately demand that Miliband follow the PM and promise to govern alone after May 2015.
Any minority government would soon collapse as there would be no impetus for the Lib Dems to support the Queen's Speech.
The party's new 404 page features Ed Balls and the message "Just like Labour's plan for the economy, this page doesn't exist."
Local voters resent outside interference and Lib Dem activists will be encouraged to rush to their leader's defence.
The Deputy PM's warning that he would "absolutely insist" that a new coalition would not "break the bank" suggests that he may push Labour to back an Osborne-style deficit plan.
At Spring Conference, some of the manifesto raw meat needs to be presented and debated.
The decision by Tim Farron and four other Lib Dems to rebel against local government cuts is a reminder of the more open debate needed about the austerity to come.
With the personal allowance already at £10,000, the lowest-paid five million workers will not benefit from further increases.
Ask any "ordinary" person what the Lib Dems have been up to in recent weeks and they'll mention the scandal.
The Lib Dems says the top tax rate will be cut "over my dead body". But he said the same about the 50p rate in 2011.