The polls suggest that on the face of it today’s byelections in Clacton and in Heywood and Middleton are going to be rather unexciting affairs. In Clacton Ukip will take their first parliamentary seat in the form of Douglas Carswell, the ex-Tory who has defected and triggered the contest. In Heywood and Middleton Labour is very likely to retain it.

But winners aside, there are other aspects of Thursday’s results which may provide some interesting signals ahead of next year’s general election.

Clacton



In Clacton, a poll by Lord Ashcroft in September had Carswell on 56%, and the Tories on 24%. According to the poll, 59% of those that voted Conservative in 2010 will vote for him on Thursday, along with 45% of 2010 Labour voters . Overall, Labour was on 16%, the Lib Dems on 2%.

Interestingly, only 37% of local voters – and 57% of Ukip supporters - said they thought Carswell becoming the Ukip MP for Clacton would make a referendum on Britain’s EU membership more likely.

An earlier poll by Survation had Carswell ahead by 44-points, on 64%. The Conservatives on 20%, Labour on 13% and the Liberal Democrats on 2%.



By comparison, in 2010 Carswell won 53% of the vote.

Heywood and Middleton



Also voting on Thursday Heywood and Middleton, where a byelection was called following the death of Labour MP Jim Dobbin. Labour has held the seat ever since the constituency was created in 1983, and is very likely to retain it on Thursday.

In case you missed it, Lord Ashcroft's snapshot poll is projecting a Labour hold in Heywood & Middleton. pic.twitter.com/DobZvPm0i7 — Britain Elects (@britainelects) October 6, 2014

In 2010, Labour won 40% of the vote, Conservatives 27%, Lib Dems 23%, BNP 7% and UKIP 3%.

The likely growth of Ukip is evident, but the party’s impact in 2015 will be less about its overall score or concentration of support, and more about where it has the opportunity to change a specific race’s outcome.

Heywood will not be one of those races.

The polls also suggest that the Lib Dems could finish behind the Greens, which would rub more salt in Nick Clegg’s wounds and suggest the same may even be possible in many constituencies in the 2015 general election. Of course, the argument of concentration and distribution of support also applies to the Lib Dems.

Coming up: Rochester and Strood



Far more interesting than Thursday’s votes, in terms of signals ahead of the next general election at least, will be the upcoming byelection in Rochester and Strood. There too the vote was triggered when the local MP, Mark Reckless, defected from the Conservatives to Ukip.

A poll by Survation has the incumbent ahead, on 40%, with the Tories on 31%, Labour on 25% and the Lib Dems on 2%. In 2010, the Conservatives won 49% of the vote, Labour 29% and the Lib Dems 16%.

If these figures were repeated on byelection day, the Conservatives would be worried as the seat hadn’t previously ranked too highly in terms of favourability to a Ukip win based on demographics.

There is an important question mark on this result happening on election day though. Mike Smithson of Political Betting spotted that nearly 25% of the Ukip support in the Survation poll were non-voters in 2010. Evidence shows that previous non-voters are less likely to vote.

This is how the figures would look with 2010 non-voters excluded:

What happens to the Survation Rochester poll when you exclude those who didn't vote last time. CON & UKIP level pic.twitter.com/Fejn4T7gUF — Mike Smithson (@MSmithsonPB) October 5, 2014

Turnout at byelections is inherently lower, so many who may not vote in Rochester in a few weeks time, may well then decide to do so next year.

Nevertheless all this adds additional layers of interest to the Rochester vote:

1. In terms of how the party will perform in a constituency where the local candidate isn’t as strong as in Clacton - 68% of respondents in Clacton say they intend to vote Ukip in large part because they have “the best candidate locally”. In Rochester and Strood, 70% of those who intend to vote Ukip like the party’s policies, 12% like Mark Reckless.

2. In providing an indication of Ukip’s ability to attract non-voters, and translate intent into actual votes.

3. And, as a working example of a constituency whose dynamics fundamentally change with Ukip’s presence, and where a relatively safe seat may become a three-horse race.

A date for Rochester’s byelection hasn’t been set yet, but a vote is expected in early November.