The primary focus of the reporting of the Barnsley Central by-election result has been on the fact that the Lib Dems came sixth. This is bad news for the party and there is no point in Lib Dems claiming otherwise.
There has been plenty of coverage of that elsewhere though. In terms of how the result may affect politics more broadly I think the fact that UKIP went from fifth last year to second with over 12% of the vote is even more significant.
It is difficult to be sure of the motivations of those who voted UKIP and doubtless some of their vote has picked up the protest element that previously would have gone to the Lib Dems. However the fact that so many people were willing to vote for a right-wing party that wishes to leave the European Union must be giving David Cameron great cause for concern. UKIP already came second in the European elections in 2009. Now they are beating the Tories in by-elections. There are predictions that UKIP could actually come first in the European elections in 2014. Given how unpopular the government may be in the run up to those elections as the cuts will have been really biting at that point I would not want to bet against that possibility. And if that, or anything approaching that happens, UKIP would have a lot of momentum behind them for the 2015 general election.
The problem for Cameron is one of simple parliamentary arithmetic. In order to form a majority government in 2015 his party will need to actually win seats. That is an unusual position for the Conservative Party in government to be in. Usually they would have a majority and if they lost a few seats they would still be able to retain power. That is not the case now. So if they find they are not just fighting Labour but also a rearguard action against UKIP in their marginal seats that could easily be the difference between getting enough seats to form a government (either in majority or in coalition) or losing power. The right wing vote could find itself split in a similar way to how the left wing vote split during the 1980s because of the SDP. It's unlikely that UKIP would win many seats or the sort of vote share nationally that the SDP achieved but they would only need to improve moderately on their 2010 showing to cause major problems for the Tories and that is looking increasingly likely.
So what is the solution? Cameron could try tacking further to the right to appease UKIP leaning voters in the hope of bringing them back into the fold. The problem with that is his coalition partners would not stand for that sort of thing for long and it could precipitate the collapse of the government at the worst possible electoral moment.
There is of course another solution to Cameron's UKIP woes. The main reason UKIP are such a problem for the Tories is because the First Past the Post system makes any voters who plump for UKIP by definition not able to support the Tory candidate in a constituency. That is why a UKIP surge is such a potential threat to them. But if the AV referendum passes then a good UKIP showing in 2015 would no longer be a disaster for the Tories. It is a fair assumption that many of UKIP's second preferences will go to the Tories. It will give right-wing voters the chance to show what they would ideally like without splitting the right wing vote and allowing other parties to come through the middle.
When UKIP were polling in the very low single figures the risk to the Tories in this respect was slight. But with their stunning Barnsley Central surge they are becoming a potent threat to the Blues retaining power.
And with David Cameron's limited room for political manoeuvre on the right I suspect he may well now secretly want the AV referendum to pass.