"In the very best of years, when you have a unified GOP, Republicans have an electoral disadvantage relative to the Democratic candidate; that's pretty clear," Fratto told CNBC's "Squawk Box."
"Trump is not going to bring unity to the party. If it's a contested convention, and it's someone else, that's not going to resolve unity either. So, [with] a divided GOP and a fairly unified Democratic candidate, I don't think this is a hard question," said Fratto, the former deputy White House press secretary and now managing director at consulting firm Hamilton Place Strategies.
Clinton notched victories in Ohio and Florida on Tuesday, two key swing states. Trump won the Florida GOP primary, but lost in Ohio to the state's governor, John Kasich.