(Reuters) - A third of Republican voters who support Donald Trump could turn their backs on their party in November's presidential election if he is denied the nomination in a contested convention, according to a Reuters/Ipsos poll. The results are bad news for Trump's rivals as well as party elites opposed to the real estate billionaire, suggesting that an alternative Republican nominee for the Nov. 8 presidential race would have a tougher road against the Democrats. "If it’s a close election, this is devastating news" for the Republicans, said Donald Green, an expert on election turnout at Columbia University. The...