"I think it is important we stop Mr. Trump," Kasich said at a press conference here. "He is not my pick for president, and you know I want to have a more positive approach to the solutions of the country."
Kasich was responding to a question about whether he would consider encouraging his supporters in Florida to vote for Marco Rubio, giving the senator an advantage in his home state and potentially blocking Trump from picking up enough delegates to clinch the nomination.
"Right now, I think they ought to vote for me," he said, before adding that he intends to spend most his time campaigning in Ohio and not the Sunshine State.
In the last few months, Kasich has been hesitant to go after Trump or any of the other candidates head-on, often lamenting the "dirt" and "mud-slinging" in politics and in this election.
"You don't beat Trump by personal attacks," he said Thursday. "The notion that you can beat Trump by calling him names, I don't think you get there that way. I'm not going there that way and I'm not using that kind of rhetoric."
But when asked about differentiating himself on policy, he acknowledged there are instances where he will contrast himself.
"I just don't want to be talking about the size of his hands or what kind of tan he has. I mean, that's not the way to get this done," he said, alluding to recent jabs at Trump from Rubio. "On a policy basis of course it's fair, and look, we are all in the heat of the battle, okay. We are all in the heat of the arena."
Kasich's comments also came hours before he was set to face off against Trump, Rubio, and Ted Cruz in a Republican presidential debate set in Detroit.
On Wednesday, Kasich openly acknowledged to NBC's Kate Snow that a contested convention is a "real prospect," adding one of his favorite lines: "I can't think of a better place for it than Cleveland. I mean, what would be better than that?"
If he won Ohio, a winner-take-all primary on March 15, a contested convention would be "likely," he said. "I went over numbers tonight. I hadn't even really looked at all the numbers. But I have to win Ohio," he told her.
On Thursday, Kasich claimed that if he wins the Buckeye State, he could campaign until the Republican National Convention in July, adding that he was there the last time a GOP convention opened without a nominee decided by the primaries.
"We are going to probably go to a convention," he said. "That's what it looks like. And it's going to be the most exciting time."
Kasich has said that if he does not win Ohio, he will exit the race.
"If I win Ohio, he's not going to be the nominee," Kasich said about Trump. "We are going to go to the convention. I'm going to be the nominee. Because I don't know whether you noticed or not - it's being held in Ohio. We plotted this all out."
For several days, Kasich has been voicing frustration with the tone of the campaign and his lack of media coverage as other candidates lodging attacks on one another have dominated news cycle after news cycle. He told reporters that he has "never really gotten to be heard in this country" and "you don't even put me in the stories anymore."
Kasich's press conference fell moments after former Massachusetts governor and 2012 Republican presidential nominee Mitt Romney laid out a scathing critique of Trump in Utah, calling the frontrunner a "phony" and a "fraud."
Kasich and Romney spoke on Tuesday, the Ohio governor told Kate Snow, he but wouldn't divulge what they talked about. But Kasich told reporters Thursday, "I already told Mitt, you don't beat Trump by personal attacks." He said he didn't have a chance to watch Romney's speech before meeting the media, however, there was a tweet from John Kasich's Twitter account signed "-John" praising Romney's remarks. Kasich's spokesman clarified that the Ohio governor was briefed broadly on what Romney said.
"I guess he lobbed a lot of criticisms at Mr. Trump, but he also went on to say, 'I would vote for John Kasich in Ohio,' which I appreciate very, very much," Kasich said. "Mitt's a good guy. He's very troubled about the direction of the country and you know, he had some nice things to say and I appreciate it very much."
This story originally appeared on NBCNews.com.