Photo: Todd Heisler/The New York Times; Video: By CNN

Mayor Tomás Pedro Regalado of Miami asked a question, through Jake Tapper, about climate change, fearing that rising sea levels as a result of climate change would cause flooding in the streets of low-lying cities, like his own.

Mr. Rubio, saying he shared the concern of South Florida’s future, gave an answer many on the Republican side agree with: that while the climate may be changing, there is no evidence that it is from humans, and there is no way to enforce the other countries of the world to comply with climate regulations.

But Gov. John Kasich of Ohio didn’t see them as mutually exclusive.

“We want all the sources of energy,” Mr. Kasich said. “We want to dig coal, but we want to clean it when we burn it.” He called for more solar energy, wind energy and developing renewables.

“You can have a strong environmental policy at the same time that you have strong economic growth,” he said. “They are not inconsistent with one another.”