Without naming Trump, Kasich responded to a question about the billionaire during a town hall forum in New Hampshire Tuesday by knocking Trump's tax plan.
"One of the people, without mentioning his name, gave us a tax plan. It puts us $11 trillion in the hole with no way to pay for it. That will be known over time, I think," Kasich said, suggesting that would be "lowering the bar" for public service.
Trump released his tax plan late last month, which would deliver sweeping tax cuts for nearly all Americans by slashing individual and business tax rates. One group, the left-leaning Citizens for Tax Justice, has estimated it would cost the federal government nearly $11 trillion over 10 years, while the conservative Tax Foundation predicts it would reduce tax revenues by more than $10 trillion over the same period when measured alongside economic growth.
Trump has insisted his plan would be revenue neutral due to economic gains under a Trump administration and because his plan also eliminates many deductions. But because he has yet to fully explain which deductions would be eliminated, it's difficult to estimate exactly how much his tax plan would cost.
A message left with the Trump campaign was not immediately returned Tuesday afternoon.
Kasich was responding to a question from a voter who noted that the leading Republican candidate "keeps shooting his mouth off, he's getting all the attention and he's doing that because of the things he's proposing."
"I think it needs to be shaken up. What's going on?" the voter asked Kasich.
Kasich, who has 6% of support in New Hampshire but just 2% to 4% nationwide according to the most recent polls, insisted that "national polls don't mean all that much."
"The only time they matter is when you try to get people to give you money and they go, well, can you win? That's the only time they really matter," he said before pointing to the grassroots operation he is building to reach the top of the polls.
"It's just hard work and you can't pay attention to all the flash and dash that's out there," he said. "I'm not going to say anything to get everybody all stoked up so I can get your vote. Then I would not be true to myself."
Kasich is hoping his bottom-up approach to politics will ultimately help him stay in the race and rise to be among the front-runners in the race. He likened the current stage in the campaign to "American Idol."
"Right now, I think we 're in the kind of 'American Idol,' maybe, quarterfinals and ultimately it gets down to fewer," he said.