Moderate Republicans are to launch a last ditch attempt to derail Donald Trump as the controversial billionaire looked set to take a giant leap toward the party’s presidential nomination in the “Mega Tuesday” primaries.
Voters in Ohio, Florida, Illinois, Missouri and North Carolina were set to make their decision in a make-or-break round of elections with Mr Trump holding clear leads in four of those states.
Ohio emerged as potentially the key battleground and the businessman remained tied in polls with John Kasich, the popular local governor.
Mr Trump cancelled a Monday night appearance in Florida and instead scheduled a last minute rally at an airport in Youngstown, Ohio, seeking to make a final push.
In Florida the home state senator Marco Rubio was trailing Mr Trump by up to 20 percentage points but vowed he would “shock the country” with an upset.
Mr Rubio made a final plea to voters, saying: “We have to win here in Florida. I’m asking you to believe in me now.”