Voters go to the polls today to choose a new MP for the constituency of Rochester & Strood in Kent.

For anyone planning on staying up, the result is expected around 3am.

The winner is a foregone conclusion. Mark Reckless will retain his seat, albeit as a member of Ukip rather than the Conservative party.

But this doesn’t mean the result won’t promise surprises. Here are five things to watch for.

1) The size of the victory

All four opinion polls conducted in Rochester & Strood since Mark Reckless announced his defection have given Ukip a comfortable lead over the Tories. The size of the lead grew sequentially from nine to 13 to 15 points, falling back to 12 points last week. Ukip will be hoping for a double-digit lead come the actual result, as this is the one thing the Conservatives – who have as good as conceded defeat – desperately do not want. They will also be hoping they deliver on expectations, unlike in the recent South Yorkshire police and crime commissioner by-election.

2) The share of the vote

Reckless won 49.2% of the vote when he stood as a Conservative at the 2010 election. Will he improve on this today? None of the opinion polls carried out in the constituency have put Ukip above 50%, though one came close with 48%. To take over half the vote would be a significant achievement for Ukip and a humiliation for the Tories.

3) The runners-up

We know the Tories will almost certainly come second and Labour third, but how low will they poll? Labour managed 28.5% in 2010. It could be that they don’t even manage half this figure today, and that would be hugely embarrassing. If the Tories end up lower than 30% – below what any of the opinion polls have suggested – it will be very damaging for the party in general and David Cameron in particular, who has made five visits to the constituency during the campaign.

4) The turnout

A total of 64.9% of the electorate voted in Rochester & Strood at the 2010 general election. Turnout in the Clacton by-election was 51%. My instinct is the figure could be lower this time, as the fading novelty of a Ukip insurgency combined with irritation at such a long campaign prompts over half of electors to stay at home.

5) The Liberal Democrats

Before today, the Liberal Democrats had contested 18 of the 20 by-elections to have taken place in this parliament. They lost their deposit 10 times. As of today, the total number of by-elections in this parliament rises to 21; and as of tonight, the number of lost Lib Dem deposits is likely to rise as well. In 2010 the Lib Dems won 16.3% of the vote in Rochester & Strood. Watch to see if the party ends up plummeting below 5%. If it does, it will forfeit its deposit and be £500 the poorer.

There are 13 candidates standing, which could mean the Lib Dems end up fifth or even sixth. Here’s the full list:

• Mike Barker (Independent)
• Christopher Challis (Independent)
• Hairy Knorm Davidson (Loony)
• Jayda Fransen (Britain 1st)
• Stephen Goldsbrough (Independent)
• Clive Gregory (Green)
• Geoff Juby (Liberal Democrat)
• Naushabah Khan (Labour)
• Nick Long (People Before Profit)
• Dave Osborn (Patriotic Socialist)
• Mark Reckless (Ukip)
• Charlotte Rose (Independent)
• Kelly Tolhurst (Conservative)

As the results will be announced in alphabetical order, we’ll need to wait until the very end of the declaration to discover exactly how far behind Ukip the Tories have come.