On the final weekend before the New Hampshire primary, former president Donald Trump and former UN ambassador Nikki Haley are escalating their attacks on each other in a contest that may determine whether Trump faces any meaningful opposition to his effort to capture the nomination.

Haley launched her most pointed attacks yet, taking direct aim at Trump’s mental acuity and fitness to serve another term as president a day after he appeared to repeatedly confuse Haley with Nancy Pelosi, the former House speaker, during his rally.

He falsely said Haley was in charge of security during the January 6, 2021, attack on the Capitol. Haley has never served in Congress and left her last government role six years ago.

“My parents are up in age, and I love them dearly,” Haley, 52, told reporters after her event in Peterborough, New Hampshire. “But when you see them hit a certain age, there is a decline. That’s a fact – ask any doctor, there is a decline.”

In recent days, Trump has directed increasingly caustic barbs at Haley, his most formidable opponent in Tuesday’s primary. And at a rally on Sunday (AEDT) in Manchester, New Hampshire, he continued to falsely accuse her of relying on Democrats to infiltrate Tuesday’s primary. (Eligibility is limited to Republicans and independent voters.)

Joining Trump onstage were leaders from South Carolina, the state where Haley was formerly governor. It’s a show of force that is intended to demonstrate his strength in Tuesday’s primary and raise doubts about the viability of Haley’s path forward in the race.

“Almost every politician from South Carolina is supporting me,” Trump boasted near the start of the event.

His campaign has sent a series of surrogates to the state to press his case and stir speculation about whom he might pick as his running mate, a way of signalling to voters that he is on a march to the nomination.