It is, intriguingly, an analysis that has entered some top Whitehall brains as well, as they try to game what government might land on their desks.
The Mayor of London urged Ukip supporters to vote for the Conservatives in The Sun on Friday, saying they “need to do the right thing for the country”.
Mr Johnson claimed a Labour government would be a “supine, useless federalist one” and that Ukip supporters should vote for the Conservatives to stave it off.
He also said his party would give people a say on Europe and immigration.
On last night’s Question Time Ed Miliband reiterated that his party would not do a deal with the SNP to secure government.
“If the price of a Labour government is a coalition or a deal with the SNP, it is not going to happen,” the Labour leader said.