In The Margins: Peterborough's Two-Horse Race

Peterborough is a seat held by the Conservatives by a majority of nearly 5,000 over Labour.

You might say it is a seat that today feels how bellweather seats used to feel.

Straightforward in a way that so few marginals are in this election: the Conservatives hold it; Labour want it. Minority parties do not appear likely to get much of a look-in.

It is a seat that Labour should have firmly in their sights, having held it comfortably in 1997 then again in 2001.

Two factors are likely to inhibit the Labour advance.

First, UKIP seem to be struggling to siphon off disaffected Tories - this is doubtless partly down to the incumbent, Stewart Jackson, not only a Eurosceptic but an MP who has demonstrated he is not beholden to the parliamentary party machine.

Second, while Labour can hoover up former Lib Dems in many marginal seats, not many people voted Lib Dem in Peterborough in 2010. Persuading voters to make the jump from Tory to Labour is a much harder task.

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As the campaign gets under way, I was interested in whether the parties' key messages are breaking through.

I asked people whether they knew which party has a "long term economic plan", and which would freeze their energy bills. (Conservatives for the first, by the way; Labour the second).

Most people did not know the answer to either question. This might surprise some Westminster journalists who tear their hair out at the way senior politicians repeat their messages ad nauseum.

Having spoken to a lot of voters, I was less taken aback that people are, in large part, not listening to the main parties.

The big question - a key question that could determine the whole election - is whether those people who have tuned out thus far will suddenly take an interest in the final weeks.

That is the sort of thing that could shift polls that have been near-static for months and even point the way to a more decisive result than the fudge that currently looks an inevitability.