Unstoppable Donald Trump will become the Republican nominee

Take a deep breath. A very deep one. In fact, if you're a student of American politics, the deepest you have ever taken.

Donald Trump will become the Republican nominee.

There we are. I said it. He's now unstoppable.

With his massive victory in Indiana - just called by the Associated Press as the votes are still being counted - he has seized control of the Republican Party.

Not exactly hijacked it, for this was a democratic vote not an act of terrorism. But the result is an existential crisis for one of America's two great parties.

Just think what Lincoln and Reagan would make of this.

A man who his rival calls a narcissistic serial liar and philanderer - a billionaire who has never held office - is now one vote away from the White House and the American nuclear arsenal.

There is still six months to go. He's up against one of the most seasoned and resilient operators in American politics, Hillary Clinton.

So, ok, you can exhale. Trump may lose.

But still. This is quite a moment.

  • Ted Cruz suspends his campaign

Ted Cruz pictured after his heavy defeat. Credit: Reuters

In the end the Trump tsunami swept all before it.

Even Ted Cruz - relentlessly ambitious and known for his supreme arrogance - couldn't halt the New York billionaire.

Cruz has overnight suspended his campaign for the Republican nomination after a heavy loss in the Indiana primary. He bowed to the inevitable: Trump has unstoppable momentum.

It is both a triumph and a crisis. A triumph for Trump's outrageously unorthodox campaign style; a crisis for a party that has now lurched out of the political mainstream.

Make no mistake about it: The Republican Party bosses are having a collective cardiac arrest.

The big question tonight - unanswered but looming large - is whether the party even tries to unite behind Trump or whether it simply splinters amid the shock of what has just happened.