Let me stress, straight away, I'm not suggesting the Tea Party are physical terrorists. But in conversation yesterday an idea occurred to me.
Suicide bombing changed the whole environment of terrorism. Suddenly we faced people for whom what had been presumed to be the ultimate deterrent - risk of their own death - held no threat. The terms of engagement changed, utterly. No one has yet worked out how to deal with it.
The Tea Party may be politically similar. As has become clear in their attitude to the discussions going on in Washington, they don't care about their chance of re-election when negotiating on the budget deficit. All they care about is killing the government. The normal sanction of political life - the loss of office - holds no threat for these people. That changes the rules of engagement. We don't know how to deal with it yet.
Both groups are extremist. Of course they're operating in radically different ways. But both have the aim of destroying what, for reasons of dogma, they consider to be the enemy which the vast majority would consider otherwise. And in the process they're quite willing to sacrifice their own selves.
It's not how we think democracy works. I'm not yet sure how we handle it.