WASHINGTON -- Former Arkansas Gov. Mike Huckabee has surged ahead of former New York Mayor Rudy Giuliani among Republican voters in South Carolina, and Sen. Hillary Clinton is clinging to a slim lead over Sen. Barack Obama among Democrats. A new McClatchy-MSNBC poll found that the GOP contest in South Carolina is more wide open than the Democratic race, with five Republican contenders bunched within 10 percentage points of one another. Huckabee is backed by 20 percent of likely GOP voters in the state. Giuliani stands at 17 percent, former Massachusetts Gov. Mitt Romney at 15 percent, former Tennessee Sen....