Despite it proving to be wholly expected, Mark Reckless’ by-election win in Rochester & Strood has re-ignited the Ukip inflation game. After a few quiet weeks, the talk this weekend has returned of “dozens” of gains at the general election and of “political earthquakes” across the country.

Ukip has never been that great at managing expectations but it excels at stoking publicity. That the two cannot be easily reconciled doesn’t seem to bother Nigel Farage and co, but as the 2015 election gets nearer some cool heads are needed in the party to assess realistically which seats it is worth targeting.

For even if Ukip manages to win as many as seven constituencies on polling day, it is still likely to be only the sixth largest party in the new parliament, ranking behind Labour, the Tories (or vice versa), the Lib Dems, the SNP and the DUP. Its arithmetical clout would not be as influential in any coalition negotiation as that wielded by the Scottish nationalists, nor would its MPs prove as conciliatory as those in the some of the smaller Northern Ireland parties.

Yet a haul of at most half a dozen seats could be the most feasible outcome for Ukip, if quite possibly an over-optimistic one.

So what might happen on polling day?

Douglas Carswell will definitely hold his seat in Clacton, and if Mark Reckless does the same in Rochester (which is by no means certain given his small majority) the party will already have two MPs to its name.

It would be embarassing for Nigel Farage if he failed to win Thanet South, where he is the official Ukip candidate. An opinion poll in July published by Lord Ashcroft found Ukip in front, but that was before Farage had been formally selected, and there have no been other polls since. Laura Sandys won the seat for the Tories in 2010, but she is not standing in 2015. Former deputy leader of Ukip Craig Mackinlay is the Tory candidate this time, meaning the contest will be between Ukip’s past and Ukip’s present.

Another likely gain is Boston & Skegness, where private polling conducted recently by Ukip suggested the party was ahead. As with Thanet South, the sitting Tory MP for Boston is standing down in 2015. Mark Simmonds won a huge majority in 2010, so a Ukip victory here would be sensational. But it’s the seat that the party is being most tipped to win – more so than Thanet South.

Thurrock is another seat where Lord Ashcroft found Ukip to be ahead back in July. It’s the second most marginal Tory seat in the country, but I’ve long thought that it would elude Labour’s grasp come the election. There’s a chance it might elude the Tories’ grasp as well, though the final result will be very close between all three parties. Ukip came fifth in 2010:

Great Yarmouth currently has a Tory majority of 4,276. It’s the kind of seat Labour would have been hoping to win were it heading for a election victory in a traditional two-party contest. Now I don’t think they have a chance. It will either stay Tory, albeit with a reduced majority, or be another shock win for Ukip. I haven’t seen the seat mentioned as an obvious Ukip target, but the party did well in the local elections in May and has just gained another councillor thanks to a Tory defection.

Finally, South Basildon & Thurrock East has been mooted as a potential Ukip gain, though the party has been having a few problems in the seat having recently de-selected its candidate.

Note that all of the above seats are currently held by the Conservatives. I’ve yet to see any Labour seat being seriously named as a Ukip target, though there has been some loose talk of Farage wanting to unseat Ed Miliband in Doncaster North while Great Grimsby gets mentioned sporadically. I don’t yet anticipate any Labour seats falling to Ukip come the election, and currently expect gains to be made solely at the expense of the Conservatives, and only in England.

Labour has problems of its own with the SNP in Scotland, but these could in part be offset by Tory losses to Ukip, which in turn would leave both major parties struggling to form the next government.

As for how that government could be formed, Ukip has so far stated it would not seek to enter a formal coalition with any party and would instead offer support on an ad hoc vote-by-vote basis. Though this again is evidence of fantasy prevailing over reality, in so far as it supposes Ukip will have enough MPs hold the balance of power. At present, I don’t think it will. The Lib Dems, the SNP and the parties of Northern Ireland will almost certainly come above Ukip in the coalition pecking order.

Although this is to assume the Tories or Labour will even want to form a coalition.