US Republican presidential front-runner Donald Trump won a crucial nominating contest in Florida on Tuesday, knocking rival Marco Rubio out of the race, but lost Ohio to John Kasich in a mixed result that set the stage for a long, bitter fight.
Trump, a businessman who hoped a sweep of five states would put him on the path to the nomination, now faces a three-way struggle with Kasich, the Ohio governor, and Ted Cruz, a conservative US senator from Texas, that could lead to a showdown at the party's nominating convention in July.
Kasich won all 66 of Ohio's delegates, giving new hope to establishment Republicans battling to deny Trump the nomination and block him from capturing the 1,237 delegates needed to win the nomination.
On the Democratic side, former Secretary of State Hillary Clinton, 68, won in Florida, Ohio and North Carolina, putting more distance between herself and rival Bernie Sanders, 74, a US senator from Vermont.
The wins for Clinton added to her lead in pledged delegates over Sanders and gave her an almost insurmountable edge over him, putting aside the memory of last week's stunning loss in Michigan. The Democratic races in Illinois and Missouri on Tuesday had yet to be decided.
As she had after other primary wins, Clinton was thinking about a possible match-up with Trump on Tuesday.
"We can't lose what made America great in the first place, and this isn't just about Donald Trump," Clinton told supporters in West Palm Beach, Florida. "We can't just talk about economic inequality, we have to take on all forms of inequality and discrimination."
Trump's vows to deport 11 million illegal immigrants, impose protectionist trade policies and temporarily ban Muslims from entering the country have rattled the party's establishment and left them scrambling to block him.
Kasich's win in Ohio will make him the prime hope of the party's mainstream leaders who fear Trump's rowdy campaign will lead the party to defeat in November, replacing Rubio.
Kasich, who has tried to emphasize a more positive approach in a Republican campaign dominated by the pugnacious Trump, said his campaign was "about holding us together, not pulling us apart."
"I will not take the low road to the highest office in the land," Kasich told supporters in Berea, Ohio. "We are going to go all the way to Cleveland and secure the Republican nomination."
The loss in his home state of Florida was a brutal blow for Rubio, 44, who was once a rising star in the party but foundered in the presidential campaign.
"While we are on the right side this year, we will not be on the winning side," Rubio, a first-term senator who is not seeking Senate re-election, told supporters in Miami as he pulled out of the race.
Rubio said the party's establishment had long looked down on conservatives and taken their vote for granted.
"People are angry, people are frustrated," he said, adding it would have been easy to stir up those frustrations and make people more angry. "I chose a different route and I'm proud of it."
Democratic presidential candidate Hillary Clinton Source: AAP
By capturing Florida, Trump won all 99 of the state's delegates, giving him a huge lift in his drive to the nomination. He also won Illinois, while no winner had emerged as yet in the Republican races in Missouri and North Carolina.
But Kasich's chief strategist, John Weaver, argued in a memo released after the Ohio result that no candidate was going to win the necessary delegates before the convention and Kasich would be the best Republican candidate against Clinton.
Trump, 69, said early on Tuesday that his momentum was already drawing in establishment Republicans who had previously balked at his candidacy but now see him as the likely nominee.
"They're already calling," he told NBC's "Today" show, without naming names. "The biggest people in the party are calling."
"I reject any effort to spread fear or encourage violence ... or to turn Americans against one another."
Democratic President Barack Obama spoke out on Tuesday, saying he was dismayed by what was happening on the presidential campaign trail.
"I reject any effort to spread fear or encourage violence ... or to turn Americans against one another," Obama, referring to Trump, said during an event on Capitol Hill.
Trump argues that his candidacy has brought a breath of fresh air to US politics and says his campaign rallies are peaceful events except for a few incidents.
Ohio voter Mark Hoprich, 51, said he likes Trump's direct manner.
"I like that he's an in-your-face type of candidate and tells it like it is," said Hoprich, who works in law enforcement.
"So, hopefully, when it comes to dealing with other countries, we could come out more on the winning side," he said at a polling place in Independence, outside Cleveland.
