Where to now for Marco Rubio and the Republican Party?

Donald Trump's controversial run to become the Republican presidential candidate received another boost with Marco Rubio calling it quits.

The presidential primary season barrelled towards a potentially decisive day that could transform Trump and Clinton from frontrunners to likely nominees.

COMMENT: Trump has turned the entire political world upside down, he's turned it into a sideshow of stylised violence, writes John Dybvig.

COMMENT: In Trump's version of events, the recent upswing in confrontation is to be blamed on professional "disrupters" who come to his rallies looking for fights.

An already ugly campaign has descended to a new level. The question now is whether it is possible to contain what Trump has unleashed across the country.

COMMENT: The Left and Right are agreed that Trump would demean the world's most prestigious political office.

Democratic presidential hopefuls Hillary Clinton and Bernie Sanders sparred over who was more committed to immigration reform at a presidential debate.

You want to be mayor? Get a wall.

A retired three-star general has spoken out that the armed forces would not be Trump's "palace guards" if he became president.

Could an old bet about Donald Trump prove lucrative for Polly Gillespie?

No precedent exists for the success so far of Donald Trump, who has been neither a state governor nor a member of Congress.

Donald Trump is responding to Mitt Romney's evisceration of him by noting that that the 2012 GOP presidential nominee begged for Trump's endorsement.

COMMENT: Every day it is less surprising that Trump does best in the areas of the country with the most racist Google searches.

Yessir, I was wrong. It's reasonable to consider Trump the favourite to win the Republican nomination for US President, writes Jack Tame.

COMMENT: The barbarian is no longer at the gate. He's inside the castle and heading for the throne room, writes Paul Thomas.

By the time you sit down to eat your turkey this Christmas, Boris Johnson and Donald Trump could lead the English-speaking world, writes Peter Foster.

Republican presidential candidate Marco Rubio has received boosts in his drive to become the mainstream Republican alternative to Donald Trump.

Hillary Clinton badly needed to win the Nevada caucuses. And she won them.

Jeb Bush's failure demonstrated money is not everything, and that, this time, solid, innovative policy is not a ticket to the nomination.