For a party that has gone to extraordinary lengths to stress its links to small business, Republicans are terrible salespeople. They have had just one task this week: to market Mitt Romney. The trouble is no one's buying it.

At first sight the problem seems to be presentational. The contributions from the stage are wooden; the jokes flat; signs of oratorical flare rare. Time and again with just a handful of exceptions, a speaker came to the podium to great cheers only to dampen the enthusiasm with their actual speech.

Yet the sense you get from the floor is of a party barely going through the motions. Missing their cues to clap and boo, they respond as though they're watching vaudeville by satellite – it's as though they're not even there. Spend an hour on the convention floor in Tampa and you'd be forgiven for thinking the Tea party has switched to decaf.