Things were bad for National in the late 70s and in the lead-up to the 80s. Robert Muldoon, then Prime Minister, supported policies that, if continued, would be utterly ruinous for the country. But die-hard National voters would continue to vote National out of tribal loyalty. And no internal coup seemed in the offing.
Bob Jones, a property investor and National Party supporter, saw the mess. He established the New Zealand Party. It ran on an economically liberal platform, in the British sense of liberal. Free markets, an end to the license raj, and a place for National supporters to place their votes if they couldn't hold their noses and vote for Labour.
Bob intended to win. He lost the election, but his policy ideas won. The Muldoonist version of National died. Labour enacted many of the necessary reforms, and National was recast in more economically liberal lines.
Trump looks as bad for the Republicans as Muldoon was for National. But lots of died-in-the-wool Republicans could never vote Democrat.
Will there be a Republican who can stand up and say that a Trumpist version of the Republican Party does not deserve to win, that the Republicans would be better losing than having Trump as its elected President, and that the Republican Party is better than appeals to tribal racism?
Americans, and Republicans who care more about free markets and free people than about having their team win any particular election, really should watch the excellent documentary on New Zealand's 1984 election, and on Bob Jones.
Trump's likely to be the nominee. More worrying is that he's trading around a 20-25% chance of winning the Presidency. Sure, it's not likely to be as bad as many might think, but that doesn't make it not-bad. Just because an electoral system is more robust to madmen than you might think is no reason to go around letting madmen become President.