As MPs decide this evening to trigger a UK general election, a key question is whether the result will be able to drag UK politics from the Brexit swamp and to a return to 'normal' politics.

The answer is simple; it depends on whether there is a clear Commons majority for a definitive position, whether that is for the current withdrawal agreement, no deal, a second referendum or a complete revocation of Article 50.

Invariably commentators pour over the finer points of polling in their quest to predict what will happen. That's the first danger of psephological speculation, offering a prediction.

Opinion polls are snapshots of attitudes not firm predictions on how voters will behave on a fixed day and after the full extent of an election is played out.

They are useful barometers of the general state of opinion rather than clear commitments on what a voter will do when election day finally comes. These caveats are important since an established trend in the polls in a pre-election period can easily change during the official campaign as voters react to specific events.

With those warning signs what can we say? Well, since Boris Johnson became Prime Minister the lead he enjoys over Labour would suggest he will win an election and then pass the withdrawal agreement so stuck at the moment in the Commons mud.

If that happens, pro-Remain parties like the Liberal Democrats and SNP could end up kicking themselves for arguing for an election which just delivered the result they most feared.

However, I would caution against drawing too much from these pre-election polls. First, they don't reflect how voters feel at the Prime Minister's failure to deliver Brexit by October 31.

Second, if the Conservatives go into an election arguing for the current withdrawal agreement they will weaponise the Brexit party with the argument the negotiated deal does not deliver Brexit.

A position of arguing for a no-deal Brexit would arguably have been easier for the Conservatives if a key objective was to give Nigel Farage no room for electoral manoeuvre.

Paradoxically, the most recent Brussels accord could actually make life trickier for Conservative candidates on the hustings as the Brexit party accuses them of surrendering to Brussels.

Farage's party have been bobbing along at 10% or just over 10% in the polls. After an onslaught against the Conservative position it is difficult not to conclude that any post agreement bounce for the Brexit party will come largely, although not exclusively, at the expense of the Conservatives.

And then there are Labour's dire poll ratings which have been stuck stubbornly in the early twenties. They will hope for a narrowing of the gap with the Conservatives and pray that a disproportionate squeeze on the Tory vote from the Brexit party will get them close to power.

On Friday I heard Corbyn loyalist Len McCluskey say bluntly it was unlikely that Labour would win an overall majority.

The Lib Dems in the UK and the SNP in Scotland are polling well. In fact they are polling far too well at the moment to see how an outright Labour majority could happen without a truly transformative election campaign.

Labour is still riding a two-horse strategy on Brexit in an appeal to a constituency which does not appear to exist. The polarised view of MPs is reflected in the wider country. Labour may feel that it has to declare for an unambiguously Remain position in the election to stem a potential haemorrhaging of voters to other remain parties.

In Scotland, the polls suggest the SNP will recover votes and seats lost at the 2017 general election. With the party looking to embolden a mandate for a second independence referendum, a strong SNP performance will make it difficult for any Westminster government to continue to say no to indyref2.

It would technically be constitutionally permissible to say no but it would lead to a stand-off of unprecedented bitterness which would lead to an inevitable debate about whether the governance arrangements in the UK can properly reflect voter priorities.

There are a number of factors that will make the coming contest fascinating. December is not the month of the year conducive to a high turnout and that would not be good when parliamentarians are seeking a mandate which has as much popular support as possible.

In the post-war period, turnouts have ranged from a high of 82.4% in 1950 to 59.4% in 2001 as a lot of electors concluded that Tony Blair's government was a cert to be re-elected.

A lot has been made about the turnout at the EU referendum in 2016. At 72.2%, it was higher than for most referenda (but well below that of the Scottish independence referendum) and it was in line with quite a lot of turnouts at a general election.

A turnout below 72% will lead to questions about 'missing voters' and to what extent polling in December on an inevitably cold day compromised every voice being heard.

Another factor that will be markedly different from 2017 will be the level of support for the two major parties. At the last election the combined support for Labour and Conservative was 82.4% of all UK votes cast. You would need to go back to 1970 for that to be beaten when Harold Wilson and Ted Heath won an astonishing 89.5% of all votes cast.

A drop in support for both major parties, a resurgent Lib Dems and a factor called the 'great unknown' hanging over the Brexit party makes the election fascinating and that's before the hurly burly of the hustings.

In short, forget the pre election polls but pay more attention to the surveys of the post-October 31 landscape. Don't take it for granted that the result will definitely break the logjam as our politics craves normality.