Real estate tycoon Donald Trump and former secretary of state Hillary Clinton tightened their grip on their respective party nominations with sweeping wins on Super Tuesday - setting the stage for an improbable match-up in November.
Mr Trump and Mrs Clinton each won seven of the 11 contests on a night when at least some of their attention appeared to shift from defeating intra-party rivals to winning the broader race.
They wasted no time in training their guns on each other as soon as early results indicated it would be a good night for both candidates.
Mrs Clinton fired the first salvo, using her speech in Florida to lay out some of the attacks against the tycoon she had first tried out in South Carolina.
"We know we've got work to do. But, that work, that work is not to make America great again. America never stopped being great," she said, in reference to the Republican front runner's "Making America Great Again" campaign slogan.
"We have to make America whole. We have to fill in what's been hollowed out."
Mrs Clinton went on to try to draw a stark contrast between her campaign and some of the divisive rhetoric that has emerged from Mr Trump's.
"Trying to divide America between us and them is wrong, and we're not going to let it work. Whether we like it or not, we're all in this together, my friends."
An hour later, when Mr Trump took to the podium at an event in Florida, he took aim at Mrs Clinton.
"She wants to make America whole again and I'm trying to figure out what that's all about. Making America great again is going to be much better than making America whole again," said Mr Trump, who otherwise appeared to be trying on a more polite tone.
And giving a glimpse of what sort of campaign he would run against the former first lady, he attacked her for being a Washington insider and also made it clear that he would argue that Mrs Clinton's e-mail scandal was "disqualifying".
For international observers, the race remains heavily focused on domestic issues. Though Mrs Clinton's foreign policy is well established from her time in the State Department, Mr Trump's is not. And he answered a question about what sort of president he would be for the world on Tuesday night by pivoting back to his domestic policy.
"I'm going to be a good president for the world but we have a country that is in big trouble. Our infrastructure is going to hell."
While Mrs Clinton and Mr Trump emerged from Super Tuesday as clear favourites, her path to securing the Democratic nomination at conventions in July is arguably less challenging than the Republican's.
The big difference between Mr Trump and Mrs Clinton in the lead- up to the conventions is that she has the backing of her party's leadership while he does not.
In fact, as Mr Trump was cruising to strong wins on Tuesday, the effort within the Republican Party to stop him gained urgency.
That afternoon, a group of high-profile Republican donors held a conference call to solicit donations for an anti-Trump organisation.
Talk is also growing of a last-ditch attempt to stop his nomination if all else fails - holding backroom negotiations at the nominating convention for all anti-Trump candidates so as to consolidate their delegates under one person.
After Super Tuesday - a day with the most number of contests on the primary calendar - the nominating race moves on to a cluster of states this weekend and next Tuesday before hitting another major milestone on March 15.
On that day, Florida and Ohio - two states seen as critical to anyone hoping to win the White House - pick their nominee.
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