David Cameron might dismiss the by-election as a typical third party squeeze, but actually there was nothing typical about this election at all, writes YouGov's Anthony Wells for Channel 4 News.

Labour wins Oldham East and Saddleworth by-election (Image: Getty)

All of the political parties can go away from the Oldham East and Saddleworth by-election quietly pleased. It was perceived as a challenge for both Ed Miliband and Nick Clegg, and both have passed.

In Ed Miliband's first electoral test as party leader Labour won the seat and increased their share of the vote by 10 points, very much in line with the position in the national polls.

For Nick Clegg, the idea of gaining the seat was relatively remote anyway. Despite the circumstances of the by-election and the Liberal Democrats being only 103 votes behind at the general election, it is incredibly rare for a party of government to gain a seat at a by-election, especially when the national polls show their support fracturing.

Under the circumstances he can be pleased that his party held their share of the vote under difficult circumstances and avoided humiliation.

David Cameron will likely be pleased for exactly the same reason - a Liberal Democrat humiliation would have put further pressure on his coalition partners, and there was no realistic opportunity of the Conservative party winning a by-election seat from third place, while in government and behind in the polls.

He can safely dismiss the drop in the Conservative party's share of the vote as a typical third party by-election squeeze.

Where he would be wrong to do so is that this was not a typical election at all - underneath the total shares of the vote the story is far more interesting.

The only reason their overall share of the vote held steady was that their loss of support was cancelled out by massive tactical voting by Conservative supporters

While the Liberal Democrats maintained their share of the vote, the polls carried out in Oldham East and Saddleworth in the last week of the campaign showed them losing a third of their support to Labour.

The only reason their overall share of the vote held steady was that their loss of support was cancelled out by massive tactical voting by Conservative supporters, where around a third of 2010 Tory voters backed the Liberal Democrats.

This is perhaps the most interesting result of Oldham East and Saddleworth - not the winner, but the new willingness of Conservative supporters to vote tactically for their coalition partner.

Of course this was an unusual contest and voters may be more willing vote tactically in the peculiar circumstances of a by-election, but it could still be a sign of things to come.

Anthony Wells is Associate Director at polling company YouGov