Donald Trump and Ted Cruz are pounding down the stretch in Iowa attacking each other on multiple fronts as they grapple for the lead with six days to go before the Republican caucuses, according to a new poll from Quinnipiac University released Tuesday. Trump has the support of 31 percent of likely caucus-goers, to 29 percent for Sen. Ted Cruz of Texas. No other candidate breaks 7 percent, the poll found. Two percent told interviewers they were undecided, but 39 percent of those who chose a candidate say they may change their minds before the caucuses next Monday....