Donald Trump's big primary victory on Saturday over Nikki Haley in her home state of South Carolina was the result of a ruthless and methodical campaign to eliminate her as a threat, according to aides and people close to both campaigns. Despite having already secured a string of primary victories, it was crucial for Trump to win South Carolina, a key early Republican primary state that often predicts the party's nominee. Unlike in 2016, Trump was facing a rival who had won two terms as governor of the state and is still locally popular.