Former U.N. ambassador Nikki Haley on Saturday aggressively questioned former president Donald Trump’s mental fitness‚ seizing on a flub at a rally in which Trump repeatedly called Nancy Pelosi by Haley’s name when attacking the former House speaker. Trump’s mix-up Friday night came as he repeated unsubstantiated claims that he made a “recommendation for troops” to be brought in to quell the Jan. 6‚ 2021‚ attack on the Capitol while Pelosi was derelict in her duties as speaker...