New entrants with big personalities and likely knife-edge result are the makings of a real blockbuster General Election

With just 100 days left to go until the General Election, chairman of polling agency ComRes Andrew Hawkins reflects on the intense, hard-fought "trench warfare" that lies ahead.

By Andrew Hawkins, chairman of ComRes

Brace yourself: the next 100 days are going to be gruelling.

This is the most uncertain General Election that anyone can remember and every politician will be fighting for every last vote.

So why is this election different?

First, the rise of the smaller parties – not just Ukip but the SNP in Scotland and the Green Party - mean that many seats which used to be predictable are far harder to call.

Second, many have yet to decide how they will vote.

Among people who tell pollsters they intend to vote on polling day, one in eight don’t know which party they will place a cross next to.

Even those who have made a choice seem unsure about it.

Half of Liberal Democrat voters say they might change their change their mind between now and polling day, as do a third of Labour and Conservative voters.

This mirrors the way voters are increasingly willing to switch political allegiance: well over half of 2010 Liberal Democrats now say they will vote for another party.

Around one in five people who voted Conservative in 2010 now intend to support Ukip. And despite picking up some new voters - most notably Lib Dem defectors, Labour too have struggled to hang on to their supporters.

Usually we have a pretty good idea of who will end up in Downing Street well before the PM asks the Queen to dissolve Parliament, which is the starting gun for the final campaign.

But this time there are very few certainties. Which is why we can expect an intense, hard-fought campaign of trench warfare.

The events which make a campaign memorable are the unexpected: think ‘Bigot-Gate’ or that Prescott punch.

Throw in a knife-edge result, a longer campaign and a credible challenge from new entrants with big personalities, and this has all the makings of a real blockbuster election.

Andrew Hawkins is the chairman of polling agency ComRes. His views do not necessarily represent those of ITV News.