(NBC) - Donald Trump says he regrets retweeting an unflattering photo of the wife of rival Ted Cruz, a rare move for the Republican front-runner more known for his boasts than backtracking. "Yeah, it was a mistake," Trump told New York Times. "If I had to do it again, I wouldn't have sent it." The retweet set off a war of words between the two candidates, and gave fresh fuel to Democratic candidates and other critics who marveled at a Republican presidential race that had descended into a fight over the candidates' wives. Trump retweeted the photo compilation showing an...