CHAPIN, S.C.  — A three-way feud among the GOP’s leading White House contenders escalated Wednesday, with Republican Ted Cruz daring Donald Trump to sue him and dismissing Marco Rubio’s charges of dishonesty just days before South Carolina’s high-stakes primary.

Yet it was Rubio who may have scored the day’s biggest win as he secured the coveted endorsement of South Carolina Gov. Nikki Haley. The popular governor said she was tasked with identifying the best candidate as she surveyed the crowded GOP field.

“If we elect Marco Rubio, every day will be a great day in America,” she said alongside the Florida senator during an evening rally in suburban Columbia.

While a major development, Haley’s endorsement did little to quiet the intensifying clash between Cruz, Trump and Rubio over alleged ethical violations in the days leading up to Saturday’s South Carolina contest.

Cruz, the Texas senator, has been trying to beat back charges of dishonesty from Trump and Rubio for weeks. He shifted his defense to the next level during an afternoon news conference that highlighted Cruz’s extensive legal training.