The Ohio governor's campaign said Kasich has no intention of dropping out of the race.
Trump deals a crushing defeat to GOP rival Ted Cruz.
Cruz is speaking to supporters at a watch party for supporters in Indianapolis.
Trump is holding a press conference at Trump Tower in New York.
"Ted Cruz is a desperate candidate trying to save his failing campaign," Trump said.
Ted Cruz and John Kasich followed with 22 percent and 14 percent, respectively.
Cruz focused on the water crisis in California at the state's GOP convention.
Massive protests disrupted Trump events this week.
Pete Wilson is set to endorse Cruz at the state's GOP convention Saturday.
The ad shows Trump defending Tyson when he was accused of rape.