President Joe Biden looked to recapture his mojo and reassured donors at a Saturday fundraiser in New Jersey hosted by Gov. Phil Murphy that he is fully up to the challenge of beating Donald Trump. “I didn’t have a great night, but I’m going to be fighting harder,” Biden told about 50 people who gathered in a tent at the back patio of Murphy’s Middletown house, overlooking the Navesink River. “Donald Trump is a genuine threat to the nation,” Biden emphasized, saying that his predecessor would undermine democracy if returned to the White House and his economic ideas would worsen inflation. The …