It is hard to over-state the significance of this nomination success for Donald Trump.
Neither of the main parties in America, the Democrats and the Republicans, have nominated anyone remotely as controversial as him since World War II.
You have to go back more than half a century, to Barry Goldwater, the 1964 Republican nominee, to find anything even approaching a parallel. Senator Goldwater was fiercely anti communist, and his opponents used an ad showing a nuclear mushroom cloud to depict him as an extremist.
The impression stuck and Goldwater was thrashed in the presidential contest against the incumbent, Lyndon Baines Johnson.
But Trump is not only extreme on issues, such as banning Muslims entry to the US, he is a non-politician, having never held elected office. He displays ignorance on domestic and international issues.
His success is unique for another reason: he has been casually and relentlessly abusive to his Republican rivals for the nomination. It is not unusual for occasional vicious or unwise comments about opponents to be made in the heat of the battle, and at times such comments are even calculated. But never in my memory of presidential elections, which stretches back vaguely to 1984 and clearly to 1988 when I spent the summer in America, has a successful nominee launched personal and cruel attacks on his party rivals.
The only Republican candidates who escaped Trump’s abuse were those who sat mute and refused to attack him, afraid of retaliation.
It will be very hard for Trump to win in November, given the huge numbers of Americans who have a seriously negative view of him. The big hope for him is that a scandal erupts around Hillary Clinton, who is also unpopular with swathes of the American public. Such a scandal might relate to her e-mails.
A third-party candidate, perhaps a moderate Republican who finds Trump repellent, should boost Clinton but this election has shown how hard it is to make predictions. The likelihood is that the Republican Party will be badly damaged by Trump’s nomination, and could even split.
Trump’s success, like that of Ukip, Jeremy Corbyn and Marine Le Pen, is part of the rise of disaffected voters across the West, as was the rise in independents in the Dail.
If translated to Northern Ireland today, the big parties would perform badly.