They know this is the most unpredictable election for decades and if the polls are to be believed no party is assured of an overall majority.
But what about the non-scientific view - studying the bellwether seats? They're seats which lead or indicate a trend in voting - going Conservative when there is a Tory majority and Labour when it's the largest party, making them a good predictor of the election's outcome.
The term comes from the Middle English bellewether and refers to the practice of placing a bell around the neck of a castrated ram (a wether) leading his flock of sheep.
So it may be ancient terminology but the bellwether tradition still seems to hold true in Kent and Sussex.
In fact during the general election of 1970, the BBC declared that "Gravesend's 80,000-odd typical electors usually do vote the way Britain votes - they went Conservative in the 1950s, Labour by a whisker in '74 and Labour more generously in 1966".
Gravesend may have changed a lot in the 45 years since the election of 1970 but one thing which has stayed constant is that voters in the constituency generally vote the way the nation votes.
Simon Atkinson, from the polling company Ipsos Mori, explains why Gravesend is such a good predictor of election outcomes.
He told me: "Gravesham is just one of those places where it all seems to fit together - it may be the demographics, the people who live there, the way they think or behave kind of matches the population as a whole - so Gravesham, Dartford are some of the really interesting places to watch.
"What happens there may well give us a guide to what's going to happen everywhere else."
Dartford has reflected the overall result in every general election since 1964 and Gravesham (and its predecessor Gravesend) has voted for the winning party - or the one with the largest share of the vote - in every election since World War One, with just one exception: 2005 - when they voted Conservative but Labour won the election.
Sussex boasts several bellwether seats including Hove, which has backed the national winner in every election since 1979 - hitting the headlines during the Labour landslide of 1997.
Legend has it that Tony Blair turned to Cherie once Labour had won Hove and said that was the moment he knew he could win the rest of the country.
Hove is currently held by the Conservatives but, like several Sussex marginal seats, Labour are determined to win it back - and many voters are still undecided.
So when voters go to the polling station tomorrow we will find out if voters in the South East's bellwether seats really can predict the outcome of this most unpredictable election.
The polls open in just over 12 hours and the party leaders are all out criss-crossing the country fighting for every last vote.