She's the seventh senator to back the Florida Republican.
"We can’t be soft and weak like our politicians,” Trump said at a Monday rally.
“I don’t think there’s anybody ... who think he’s the most electable now," Christie said.
"If he came looking for a job, you’d say, 'No thank you.'"
Willey, a former White House volunteer, alleges Bill Clinton groped her in 1993.
"It's not comfortable for me to attack Marco Rubio," Bush added.
The former president also attacked the senator's healthcare and campaign finance.
Sanders leads Hillary Clinton by a 16-point margin in new poll.
Bush and Kasich are the only other candidates with double-digit support.
Cruz said forcing women into close combat is "wrong" and "immoral."