By James Oliphant MANCHESTER, New Hampshire (Reuters) -Donald Trump, the former president, won his second straight nominating contest over challenger Nikki Haley, the only other Republican left in the race, by besting her in Tuesday’s New Hampshire primary. Haley, who served as Trump’s ambassador to the United Nations, was attempting to keep the margin close in order to argue she has a viable path forward. Meanwhile, President Joe Biden easily won the Democratic primary, even though he wasn’t officially on the ballot. Here are takeaways from the New Hampshire primary: A PRICKLY PATH It was oft…