Do UKIP's threats to scupper the Smith package with an "Axis of EVEL" have the slightest credibility?

UKIP's David Coburn, aka "the Pride of Scotland", renowned for brilliant insights such as his claim a few months back that the No-supporting Herald is "an SNP paper", has now decreed that the Smith package is already "dead" because UKIP will block it if they hold the balance of power.  This does of course imply that UKIP are best-placed to hold the balance of power in the event of a hung parliament, as opposed to the reality of current seat projections which show them limping to a distant fifth place in the next House of Commons - behind both the SNP (who are projected to be in third place) and the Liberal Democrats (who are projected to be in fourth place).

But projections are only projections, and the relative fortunes of the parties could still change in the five months between now and the general election.  So what are the real chances of Coburn being able to thwart our dreams (ahem) of full Smith implementation?  To be fair, there have been a couple of individual polls in recent weeks putting UKIP well into the 20s, which would be enough to secure them more than 100 seats.  If that turned out to be the result, all bets would be off - UKIP would have a very real chance of being able to dictate government policy to a significant degree.  But the polls that pointed to that outcome look like outliers, so to get there Farage would probably have to gain a few extra percentage points of support, perhaps courtesy of his potential inclusion in the TV debates.  It's just about plausible that he could pull that off, but the nature of first-past-the-post elections means that it's almost all-or-nothing for him - if he fails to get UKIP well into the 20s, they're not only likely to fall short of 100 seats, but will probably have no more than 12.

It's not impossible to have a big say over government policy with only 10 or 12 seats, but the window of opportunity is extremely narrow.  The only way it could happen would be if the Tories are the largest single party, short of an overall majority, but only just short.  There's no way that UKIP can engineer that outcome - they'll be relying on pure luck.  And even if it does happen, it's quite likely that the Tories' first port of call would be the Liberal Democrats, and would only turn to UKIP as a last resort if negotiations with the Lib Dems fail.

So when you take all of the above factors together, I'd say that Coburn's chances of being able to carry out his threat are probably 10% at best.  Whether that's a good or a bad thing for the Scottish national movement is obviously open to debate.  After all, it's hard to think of anything more likely to produce a decisive surge in favour of independence than a Tory/UKIP "Axis of EVEL" denying Scotland what had been firmly promised only a few months earlier.