Donald Trump's rival Marco Rubio urges tactical voting to stop front-runner
Republican presidential front-runner Donald Trump is calling for the party to unite behind him, but opponents are taking unusual steps to block him from victory in critical primary states Ohio and Florida on Tuesday.
On Friday, Florida senator Marco Rubio urged voters in Ohio to cast ballots for fellow challenger John Kasich, the state's governor.
"If you want to stop Trump in Ohio, Kasich's the only guy who can beat him there," Rubio spokesman Alex Conant said.
In turn, Mr Rubio is hoping to win in his home state, splitting the day's two big delegate prizes and keeping them out of Mr Trump's hands.
While only Mr Kasich can take on Mr Trump in Ohio, "Marco is the only guy who can beat him in Florida," Mr Conant said.
Polls suggest Mr Kasich has a better chance in his state than Mr Rubio has in Florida, but it is important to both of them, and to other remaining candidate Ted Cruz, to keep Mr Trump from sweeping the two big states and taking a big step toward securing the Republican nomination.
But Mr Trump picked up an endorsement on Friday from one-time rival Ben Carson.
The developments came a day after a surprisingly civil Republican debate in which Mr Trump warned the party to end its civil war over his candidacy and to "be smart and unify".
While the debate focused on issues rather than insults, it was not clear that Mr Cruz, Mr Rubio or Mr Kasich were able to gain ground on the New York billionaire.
In all, 367 Republican delegates are at stake in Tuesday's voting that also takes place in Illinois, Missouri, North Carolina, and the Northern Mariana Islands, which could go a long way toward determining the Republican nominee.
In the race for Republican delegates, Mr Trump has 459, Mr Cruz 360, Mr Rubio 152 and Mr Kasich 54. It takes 1,237 to win the Republican nomination for president
Democrats Hillary Clinton and Bernie Sanders also will be competing on Tuesday, with Mrs Clinton out to regain momentum after her startling loss to Mr Sanders in Michigan this week.