By Tim Reid and Nathan Layne DES MOINES, Iowa (Reuters) -Florida Governor Ron DeSantis and former U.N. Ambassador Nikki Haley repeatedly accused each other of lying in an acrimonious debate that mixed policy with insults as the two candidates battled to emerge as the top alternative to Donald Trump days before the campaign’s first votes are cast. But with the former president absent once again from the debate stage, the rivals aimed most of their ammunition at each other, rather than the clear frontrunner in the race. “We don’t need another mealy-mouthed politician who just tells you what she …