One Republican senator said if Trump were to drop divisive subjects, such as his claim that Mexico has purposefully sent its criminals across the southern border, and focus exclusively on the economy, he’d have a better chance of winning in November.

“If he were to just hit the economy every day and stress his business background and say Hillary Clinton’s just more of the same, you never know,” said the senator.

Lawmakers also want Trump to change his tone, which so alienated rivals that leading party figures such as Mitt Romney and the Bush family, which includes two former presidents, have so far refused to endorse him.

“I need to hear more from Donald Trump on his vision for this country beyond his slogan and he needs to articulate what a Trump presidency would look like,” said Sen. Susan Collins (R-Maine).

“He also needs to knock off the gratuitous personal insults and to do a lot more outreach, including to the Muslim community.”