One of the most polarised polls in US history entered a decisive phase today with a five-state vote as Republican front-runner Donald Trump looked to seal party nomination while Democrat Hillary Clinton faced stiff challenge from her rival Bernie Sanders.
Voting was underway as five delegate-rich states -- Florida, Illinois, Missouri, North Carolina and Ohio -- hold their Republican and Democratic primaries.
In the Republican caucus on the Northern Mariana Islands, Trump posted a big win bagging almost 73 per cent of the vote. He will get all nine delegates from the US territory. Texas Senator Ted Cruz came in second with 24 per cent.
A big win on 'Super Tuesday 2.0' for Trump, 69, as latest polls indicate, could very well bring the billionaire real estate magnate very closer to the magical figure of 1,237 delegates needed to win the party's presidential nomination for the November 8 election.
For Republicans dead set on stopping Trump, 'Super Tuesday 2.0' represents a final chance to seriously impede his path to the party's presidential nomination.
Raising the stakes on the Republican side is that Florida, with its 99 delegates and Ohio, which awards 66 delegates, are winner-take-all contests.
That means for the two home-state candidates, Ohio Governor John Kasich and Florida Senator Marco Rubio, anything short of wins in their own backyards could leave them so far behind in the delegate count that they would face intense pressure to end their campaigns.
A sweep by Trump would mean all that would be left are extraordinary measures -- like a contested convention. And even that could be out of reach.
Texas Senator Ted Cruz, Trump's nearest rival, does not lead the polls in any of the five states, but the contests will once again test the strength of his campaign's data and organisational capabilities.
There are opportunities for Cruz to rack up delegates -- particularly in down-state Illinois congressional districts, Missouri and North Carolina. His campaign has been carefully calibrating his schedule to seize on those opportunities -- which means he will try to stay close to Trump in the delegate count even without winning a state.
On the Democratic side, Clinton is all but assured of finishing her sweep of the South by picking up wins in Florida and North Carolina.
The real battleground will be the Midwest. Sanders will try to replicate his stunning victory in Michigan last week by winning similar big, manufacturing-heavy, states -- Illinois, Missouri and Ohio.
It is an especially important set of contests because Clinton's allies hope she can deliver a knockout blow before the race shifts west, to states where Sanders expects he will be more formidable.
Trump, who has so far won primaries and caucuses in 14 states is said to be the favourite in Florida, North Carolina, Illinois and Missouri, while in Ohio he is locked in a neck-and-neck fight with Kasich.
