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In Ohio, the controversial businessman bests Kasich by a smaller margin of 6 points, 41 to 35 percent, with Cruz at 15 percent and Rubio at 7 percent.

Florida and Ohio are key for Republican rivals who are hoping to keep Trump below the necessary 1,237 delegates for the nomination, forcing a brokered convention over the summer.

The winner-take-all contests on March 15 in Florida and Ohio have 99 and 66 delegates up for grabs, respectively. Voters in Illinois, North Carolina and Missouri will also cast ballots next week.

Rubio's campaign has insisted that it is putting its focus on winning Florida. The senator failed to win any delegates in the four states that held voting on Tuesday, placing fourth behind Kasich in Michigan and Mississippi.

Sanders had a surprise showing Tuesday in Michigan to win that state's primary, while Clinton expanded her delegate number by picking up support in that state and dominating in Mississippi.

The CNN/ORC surveys of 313 likely GOP primary voters and 264 likely Democratic primary voters were conducted March 2–6. In Florida, the margin of error is 5.5 points for Republicans and 6 points for Democrats, while in Ohio it is 5 points for Republicans and 5.5 points for Democrats.