The thing that should scare both Labour and Tories alike is that the Liberal Democrat surge has little to do with its policies.
Both big parties are now responding with strategies which will not openly attack Nick Clegg personally (recognising that this would work against them) but attempt to pick apart the Liberal Democrat manifesto on Trident, migration, crime, and their plans for the economy – with a bit of scaremongering about a hung parliament for good measure.
Some newspapers too, are attempting to show by polling , that the Liberal Democrats' policies are not that popular.
It is still unclear however, underlying last week’s TV debate (and it should be noted that according to an ICM poll  the Lib Dem surge began before it) what the reasons for the poll boost actually were. Was it a Damascus Road experience, where everyone suddenly saw the Liberal Democrat manifesto in all its glory?
Probably not. On policy the Liberal Democrats do not differ greatly from the ‘Labservatives’. It is more likely that the surge is down to a number of factors coalescing - including people’s disillusionment with politics generally, the MPs' expenses scandal, the cult of celebrity, blame for the economic crisis and the desire for change (and a whole lot more). The TV debate was the catalyst which made the various ingredients respond together, causing the reaction to take place. The Liberal Democrats entered public consciousness in a new way as something which could harness the energy, give expression to the various elements, and channel them in a certain direction. And the tactic of belittling, marginalising and ridiculing the third party - which had previously held the Liberal Democrats firmly in their place - could no longer be sustained in the heat of the full public gaze.
And if this is the case, the two big parties have got a real problem. The genie is out of the bottle and Clegg is successfully harnessing the 'anti-politics' sentiment. This is a huge challenge for the both Labour and Conservatives whose traditional approaches reflect the 'old politics' against which people's rage is directed. Any attack – whether it be about policy or personality – may only serve to reinforce the Liberal Democrat position. It may simply confirm existing feelings about the old system, and the belief that it must change - with the Liberal Democrats being the ones to bring it about.
And this is crucial. There is an appetite for something new. The comparisons with Obama are important in understanding what is going on. There is a feeling, albeit not articulated in the terms that it was during the US election, that “Yes, we can”.
Brown and Cameron may try to scare people with a doomsday scenario about a hung parliament, but actually a minority or coalition government seems to be what people want in increasing numbers, according to the polls at least. In a variation on the words of Gordon Brown, they have taken a long hard look - and then a second look - at both the big parties, and they have not liked what they saw. They want politicians who can work together. And the electorate, after all, are supposed to be the bosses.
They want smaller parties to at least have a say in how the country is run (something which perhaps even the Conservatives spotted with their ‘invitation to join Government’). They want serious electoral reform which means not just that smaller parties have representation, but that a party which comes third in the overall share of the vote doesn’t get the most seats in the House of Commons. They want an end to governments who are elected by just 20 per cent of the adult population, having majorities in the House of Commons which mean they can drive whatever they like into law. They want an end to promises which are dropped when a party enters office. Most of all, they want to give the system a good kicking and a good shake – in a way they thought they were doing to the Tories in 1997.
This is a movement, rather than a party political phenomenon. And that is threatening to the parties because no one really controls it. Clegg is the manifestation not the cause. The Liberal Democrats are one big vehicle, but not the driver .
Of course, if after May 6th 2010 we get a hung Parliament, there will be problems. There will be disillusionment and pain. This is not a new heaven and a new earth. No system is perfect. But it may be of a different variety to that we have already experienced for decades. And it may well deliver significant change for the better. This is what people are hoping for.
But the system is strong – and it will fight back with a vengeance over the next two weeks. Its underlying agenda is to strip the Liberal Democrats of credibility, as it has always tried to do. So the real challenge is for Clegg. Will he walk the talk and rise above it? Will he respond in an opposite spirit? Will he demonstrate in his actions the new politics, or will he (as he has already done  during this election campaign) resort to the tactics of his opponents? He can either ride the wave, or fall off his surf board of opportunity and drown.
The policy debates are not unimportant. Clegg needs to reinforce difference and the idea that he is the ‘change candidate’. In response to the attacks, he should make the case for ‘good migration’. He should be clear in asserting how Trident is a relic of a bygone age which makes the world less safe, and how a criminal justice system based on longer prison sentences and harsher punishments is no antidote to crime. He should propose that the best way to support soldiers is to bring them home from Afghanistan, and emphasise his opposition to the inavasion of Iraq. He should push for a green economy and make the case for a fairer electoral system in which everyone has a stake.
But the crucial weapon in his armoury is hope. Clegg needs to show that the new politics is here to stay if he is to achieve his goal of a hung parliament in which the Liberal Democrats are the changemakers.