Despite talk of bringing down the political elite, the ConLabs may still have the last laugh

At the last general election in 2010, over a third of voters did not vote Conservative or Labour - two-thirds of whom voted Liberal Democrat.

Since that time, we have seen a decline in the Liberal Democrat vote, along with a rise in other parties - UKIP are propelling forwards constantly in the 15-20% mark, the Greens are making good progress overtaking the Lib Dems in some polls, and the SNP, despite a failed referendum campaign, are going from strength to strength in Scotland. Meanwhile, Plaid Cymru are still campaigning hard, and of course there are the parties from Northern Ireland. At the time of writing, there are 11 different parties with MPs in the House of Commons.

Polls show the combined ratings of the Conservative and Labour parties (the 'ConLabs') hover around the early 60s - the lowest for about 100 years.

This has caused much excitement in the circles of some political observers. There is talk of no party ever having a majority again, of multi-party politics, of coalitions with two or three parties becoming a permanent feature, of smaller groups talking about the balance of power.

However, there is a huge stumbling block. It is our old favourite - the electoral system - the most formidable protector of the two party consensus. While the ConLabs may fall even below 60%, it looks quite possible that their share of the seats will go above 90% for the first time since 1992.

Firstly, the Liberal Democrat decline. Predictions are that they will lose at least a third or even over half of their 57 seats won in 2010. Who will pick most of those up? That's right - the Conservative or Labour parties, with maybe a few to the SNP.

Secondly, UKIP. They have the famous problem that the old Liberal-SDP Alliance struggled with. How to turn votes into seats. Despite the two by election wins, hundreds of councillor victories, and a consistent poll showing in the high teens, latest indicators are that even Nigel Farage will struggle to get into parliament. It is quite possible, after a four week campaign of talk about the government, that UKIP will be squeezed in the classic smaller party tradition and come away with very little, if anything.

Thirdly, the Greens. They have the same problem on a much smaller scale. Their main targets are to hold Caroline Lucas's seat and taking Norwich South - but both are top targets for Labour, the latter will almost certainly go red.

It is quite possible that UKIP and the Greens will get over 20% of the vote between them without a single seat to show for it.

Finally, the SNP. They have an advantage in that, unlike UKIP and the Greens, their support is more concentrated. But you can be sure the general election campaign will focus on who is the UK government - Conservative or Labour. Many SNP supporters may vote Labour to keep the Conservatives out. Indications are that SNP will make some gains - but probably not as spectacular as some of the headlines say.

So the overall question is - will the number of Lib Dem losses exceed the SNP gains? If the answer is yes, then the likely consequence is to increase the number of seats held by the ConLabs.

There will still be a good spread of 'other' MPs of course, and whether there is a hung parliament will depend on how close the Conservative and Labour parties are to each other, but if one of them has a majority, and there is a substantial increase in the number of seats they hold, you can imagine the pleased and smug expressions from the politicians and the media at the re-assertion of the poltical establishment.

Sorry, small parties, they will all say. You have had your fun, but you can't beat the system. It's two party politics, old boy. Back to business as usual.