The by-election in Rochester and Strood in north Kent is the 21st contest for a Westminster seat since the last general election in 2010.
In nearly half of those races, the story of the by-election has been UKIP: they have finished second in eight, won one - and are on the brink of winning another.
UKIPFor a party that began life in a dusty office at the London School of Economics, when Sir John Major was prime minister, it has been quite a couple of months.
What began as the Anti-Federalist League in 1991 became the UK Independence Party - and is now making the political weather.
But for years, the itch UKIP just couldn't scratch was winning a seat in the Commons.
Now, just 42 days after taking their first seat, when Douglas Carswell won Clacton in Essex, opinion polls and politicians on all sides expect them to win again in Rochester and Strood.
Psychologically, a UKIP victory will be hugely important to the party. Some discounted UKIP's breakthrough in Clacton as an inevitable consequence of being verdantly fertile territory for Nigel Farage's outfit.
But expect UKIP to remind us regularly that Rochester and Strood is only 271 on its list of winnable seats, when Clacton was first. 'There is no such thing as a safe seat,' may just be a sound bite you catch tumbling from the mouths of celebrating Ukippers, if they win again.
ConservativesMark Reckless really did pick his moment to tear up his long-held Conservative Party membership card, sign up to UKIP and call a by-election in Rochester and Strood.
It was just as UKIP's conference in Doncaster was concluding, and the Tory conference in Birmingham was beginning.
So Conservatives arrived in the West Midlands with smoke coming out of their ears and some choice words emerging from their lips.
The prime minister wasn't immune from a blast of robust language, promising to 'throw the kitchen sink' at the by-election contest to prevent Mr Reckless getting 'his fat arse back onto the green benches' of the Commons.
And yet, despite five campaigning visits from Mr Cameron himself, Mr Reckless's posterior, large or otherwise, does appear destined to be reunited with the green leather of the Palace of Westminster.
So what happened to the kitchen sink? I was a regular visitor to the constituency throughout the contest and while the Tories did throw a fair bit of crockery at their campaign, it felt like the kitchen sink remained plumbed in Westminster. They seemed to clock fairly quickly that, despite their early bravado, they weren't going to win.
Assuming they are beaten again, expect the game of 'who's next?' to begin in earnest. Which other Conservatives might be tempted to leap over to UKIP?
LabourAfter the turbulence for Ed Miliband of the last few weeks, Labour crave the spotlight and the jitters transferring to the Conservatives for a bit.
The party has been going out of its way to label this by-election as a two-horse race. That is the polite way of saying 'don't expect anything from us, we've just turned up to make up the numbers'.
And yet, this is a constituency that straddles the River Medway: Strood on its north bank, Rochester on its south. Ask any elections nerd what the word 'Medway' means and the word 'bellwether' will likely quickly follow: the towns along this river tend to pick the winner at general elections.
In other words, it is the kind of place Labour might expect to do better.
Until 2010, there was a Labour MP here. Ah, different constituency boundaries, the party says. True. And Labour don't need to win this seat to win the general election. But, nonetheless, expect at least some of the analysis after the result to focus on just what sort of third place Labour manages, if indeed they do finish third.
A credible third will be fine for Ed Miliband, a best-of-the-rest distant third, or worse, with a measly share of the vote will be leapt on by his opponents in order to re-start those arguments about whether he is up to the job.
Liberal DemocratsThe Lib Dem candidate Geoff Juby has been the political equivalent here of the Philae Lander on Comet 67P.
Apparently billions of miles away from support from HQ and reliant only on his own batteries. Whilst the trains from London have carried Cabinet ministers and their shadows, and Ukippers by the carriage-load, the Liberal Democrats haven't bothered.
Councillor Juby has had nothing but his giant yellow rosette and a handful of plucky local activists to help him. But, there is a clear-headed strategy behind what looks like meek surrender to another ritual whacking at the hands of the electorate.
Rochester and Strood is no-hope territory for them, so precious general election funds are best saved to be spent in seats in the coming months where they have a chance of clinging on.
The Green PartyThe Greens are upbeat. The party is riding high - for them - in the polls.
A YouGov poll for The Sun earlier this week put them on 8%, the highest they have ever managed with that pollster.
Activists don't miss a chance either to talk about their rising membership numbers, now standing at almost 27,000, a figure up 87% since January of this year.
All that said, they will almost certainly be also-rans in Rochester and Strood. When I asked their quick-witted candidate Clive Gregory how he approached campaigning in a seat that is not one of their targets he shot back: 'Well, it is a target for me!' That was me told.
For them, it is all about getting the Green message out, talking up what they see as a 'Green surge' and putting in a performance that helps with their campaign against the broadcasters for excluding them from their planned general election debates.
Entities 0 Name: Rochester Count: 7 1 Name: UKIP Count: 6 2 Name: Strood Count: 4 3 Name: Reckless Count: 2 4 Name: Clacton Count: 2 5 Name: Ed Miliband Count: 2 6 Name: Nigel Farage Count: 1 7 Name: Labor Count: 1 8 Name: YouGov Count: 1 9 Name: John Major Count: 1 10 Name: Geoff Juby Count: 1 11 Name: Douglas Carswell Count: 1 12 Name: Philae Lander Count: 1 13 Name: Conservative Party Count: 1 14 Name: Cabinet Count: 1 15 Name: UK Independence Party Count: 1 16 Name: Mark Reckless Count: 1 17 Name: Birmingham Count: 1 18 Name: Tories Count: 1 19 Name: Green Party The Greens Count: 1 20 Name: Medway Count: 1 21 Name: earnest Count: 1 22 Name: Green Count: 1 23 Name: River Medway Count: 1 24 Name: Liberal Democrats The Lib Dem Count: 1 25 Name: Clive Gregory Count: 1 26 Name: West Midlands Count: 1 27 Name: London School of Economics Count: 1 28 Name: Essex Count: 1 29 Name: Liberal Democrats Count: 1 30 Name: London Count: 1 31 Name: Cameron Count: 1 32 Name: Juby Count: 1 33 Name: Doncaster Count: 1 Related 0 Url: http://ift.tt/1r3BzNx Title: Anti-EU party set to win second UK parliament seat in blow to Cameron Description: Credit: Reuters/Suzanne Plunkett Gulpreet Baines, 18, sets fire to a United Kingdom Independence Party (UKIP) rosette, on polling day in Rochester's by-election, November 20, 2014. With distrust of mainstream parties and anxiety about immigration rising, opinion polls suggest UKIP, the United Kingdom Independence Party, will easily win a special election in the southeast English constituency of Rochester and Strood.