I haven't chimed in on the interesting results from last month's EU elections, where the anti-EU UK Independence Party won the most votes, pushing the establishment Conservative and Labour parties into a tight race for second in the voting. This American Spectator piece casts the UKIP as a loose analog of the Tea Party.
There's a difference between the countries' party systems and between the EU elections and parliamentary elections. Both point to differences in how the Tea Party and UKIP have to navigate.
We have primaries to fill most election spots in the US, so a too-moderate candidate can be challenged by a more ideologically robust one in a primary; assuming that the successful insurgent can win the general election, a faction at odds with the establishment of their side of the political spectrum can place people in the legislature without having to form their own party. British parties, with candidate selection largely centralized, are harder for insurgents to get a toehold in.
In a two-party system with winner-take-all elections, you need a plurality of votes to get a seat; a third party, unless they attract folks from both existing parties, is more likely to split the votes on its side of its side of the aisle, allowing the other side's main party to win. Thus, an independent Tea Party would have a hard time beating back both a moderate Republican and a Democrat in a general election, winning only in very conservative areas where Democrats aren't much of a factor.
The advantage that UKIP had in last month's EU elections is that those are run on a proportional-representation system, where 28% of the votes will net you about 28% of the seats. 28% would be unlikely to win too many places outright, but they managed to get a plurality of the votes in the country with votes split at least four ways with the existing three main parties in England and five ways with left-leaning nationalist parties in Scotland and Wales.
In a general election, UKIP has to field a slate of candidates, one for each seat, each who will have their history mined for embarrassing quotes by the rest of the field. They also have to get a plurality in a given district to win that seat. That's an uphill climb that will be hard to do.
Not impossible. On a more local scale, I'm reminded of the ADQ in Quebec that looked to be Francophone and somewhat libertarian in contrast with the Liberals and the rather statist PQ. They did fairly well in one election cycle, but a raft of rookie legislators made them shrink back to much smaller levels and were later absorbed into the CAQ led by some veteran but center-right Pequistes.
The ADQ wasn't ready for prime-time, and the UKIP may well not be. However, the existing British parties don't address the folks who are getting the short end of the EU's centralization of policy-making.
What could be interesting is if the UKIP gets enough seats to deny either the Conservatives or Labour a majority. If the Liberal Democrats continue their meltdown, the two options in such a hung parliament might be a UKIP-Conservative coalition that moves policy towards separation from the EU or a Tory-Labour establishment-maintaining package.
The lion share of the British and world media will be screaming for the latter option, painting the UKIP as untouchably racist and radical. Thus, a "grand coalition" of the two establishment parties, as has been the norm in Germany as of late, will be the likely result of a UKIP emergence, unless they somehow manage to get a majority or so close to a majority that patching together a coherent government without them would be impossible.
It will make British politics a bit more interesting and a bit more fluid. An analogy that comes to mind is the quick rise of the New Democrats in Canada in overtaking the Liberals as the main party of the left. However, the Dippers were a long-established party with a solid but niche following going into the last election, whereas the UKIP doesn't even have one seat in parliament right now.