My column for the FT this week asks whether the tea party will help or hurt the Republicans. The answer depends on timescale, I think. In the short term, the benefit of energy and anti-incumbent fury is mostly bad news for Democrats, Delaware notwithstanding. Beyond the mid-terms, the answer is much less clear. In 2012, the Republicans will need a positive agenda capable of appealing to the middle of the electorate, and the tea party is going to make that harder, if not impossible, to achieve. The question whether the movement is capable of tactical restraint--capable of reaching out to, and compromising with, moderates--is now very much in doubt. Scott Brown is Massachusetts suggested one answer, Delaware another.

The challenge for the Republican party was to harness the insurgents' energy and enthusiasm without being co-opted, and hence crippled. Make no mistake: a Tea Party takeover would ruin the Republicans' electoral prospects. The insurgents' agenda, in so far as they have one, is far to the right of mainstream American opinion. The US is a moderately conservative country, pleased to see the Democrats meeting resistance, but that is as far as it goes. The Tea Party's apparent desire to dismantle the federal government is not widely shared. Ms Palin's national approval ratings are far lower than Mr Obama's.

To serve the Republicans' purpose, the Tea Party had to be kept in check - and in Delaware it ran riot... Even if Delaware is the exception, the party has reason to worry. The risk is that centrist and independent voters may be so alarmed by the Tea Party's influence that they will think twice about voting Republican in November. The main threat to the Democrats this year is disappointed swing voters - centrists who voted for Mr Obama and feel let down. The Republican party was already too conservative to win their votes every time. If the Tea Party pushes Republicans even farther from the middle, swing voters may prefer not to vote at all.

Between now and the election, much will depend on the role Ms Palin and her disciples play on the national stage, either by choice or by media request. Centrists will want to know: is this the new Republican party? For the moment, polls show that independents continue to back Republican candidates: the Tea Party's victories are seen as merely local upsets. But this could change.

After the election, it most likely will, and the Republican party will then face its real test.

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