Donald Trump speaks during a campaign rally raising funds for US military veterans at Drake University in Des Moines, Iowa on January 28, 2016.  US Republicans scrambling to win the first contest in the presidential nomination race were gearing for battle at high-profile debate in Iowa, but frontrunner Donald Trump is upending the campaign by defiantly refusing to attend. Trump's gamble has left the presidential race in uncharted waters just days before Iowans vote on February 1, insisting he will not back down in his feud with debate host Fox News.Instead,  the billionaire has doubled down, hosting a rogue, rival event for US military veterans at the same time that his own party is showcasing its candidates for president to all-important Iowa voters.  / AFP / William EDWARDS        (Photo credit should read WILLIAM EDWARDS/AFP/Getty Images)