David Frum looks at the GOP’s impending defeats in New York and New Jersey, and the angry conservatives who are going to cut off their noses to spite their faces: Prelude to Republican fratricide.

What lessons will Republicans draw? You might think that the impending defeats in New York and New Jersey would drive home the need to broaden the Republican coalition. A candidate like Hoffman would have been the better candidate for New York’s 23rd CD; a candidate like Daggett the better candidate for suburban New Jersey. Republicans have to find ways to accommodate both types of candidates and both kinds of constituencies.

But the risk is that the party will draw a very different conclusion. From the New York experience, Republicans will be tempted to draw the lesson: Always nominate the more conservative candidate. From New Jersey: We need to drive pro-environmental fiscal moderates out of our party and into the Democratic Party where they belong!

And if the Republicans pick up an Arkansas Senate seat and a dozen blue-dog Democratic House seats in 2010, you can see this “tea party” mentality taking strong hold of the GOP in the run-up to 2012.

But a political formula that encourages Republicans to write off the suburbs, the Northeast, and California is not a formula for a national majority. It’s a formula for a more coherent, better mobilized, but perpetually minority party.