WASHINGTON (Reuters) - Republican presidential front-runner Donald Trump on Monday warned Republicans against backing a third-party candidate should he win the party’s nomination, saying doing so would hand the election to the Democrats. “Democrats are going to win almost certainly,” Trump said at a news conference in commenting on the prospects of Republicans trying to coalesce around a third-party candidate to prevent him from winning office. “You can’t be that spiteful because you would destroy the country.” 